How to Make a Unicorn Cake with Rainbow Layers
A unicorn cake brings together several useful decorating skills: stacking level layers, applying a crumb coat, frosting the cake, and piping buttercream rosettes. The horn, ears, and eyelashes establish the design, while the colorful buttercream mane gives you room to practice with different star tips.
This tutorial uses white boxed cake mix divided into four colors, white buttercream for the outside, and colored buttercream for the decorations. You can follow the bright pink, yellow, green, and blue layers shown in my original cake or choose your own color combination.
What You Need to Make a Unicorn Cake
Have your pans, cake board, and decorating supplies ready before mixing the batter. Your cake board should be large enough to support the cake and leave room for the piped border.
Ingredients and Decorations
- Two boxes of white cake mix, plus the ingredients required on their packages
- Vanilla buttercream for filling, crumb coating, frosting, and decorating
- Gel food coloring for four cake colors and your buttercream colors
- A food-contact-safe unicorn topper set with a horn, ears, and eyelashes
- Sprinkles, optional
The cake mix package determines the additional ingredients and oven temperature. Buttercream needs will vary with the cake’s diameter, filling thickness, and amount of piping.
Equipment
- Shallow round layer-cake pans
- Hand or stand mixer
- Four bowls for dividing the batter
- Mixing spatulas
- Offset spatula
- Cake scraper, optional
- Cake turntable, helpful
- Piping bags
- Star tips, such as sizes 14, 18, and 21 used in my original class
- Compatible couplers, optional
- Scissors
- Cake board or drum
- Cooling rack
An 8- to 10-inch board was listed in my original class materials. Choose a board that fits the pans you are using rather than treating the board measurement as the cake size.
Plan the Cake in Two Stages
Bake, cool, and chill the layers before decorating. Trying to fill and frost a warm cake can soften the buttercream and pull crumbs from the layers.
For a more manageable project, prepare the cake layers first and decorate them in a separate session. You can also practice the piping on parchment paper before working on the cake.
How to Make a Unicorn Cake Step by Step
1. Prepare and Color the Cake Batter
Prepare the white cake mixes according to their package directions. Divide the batter evenly among four bowls so the finished layers will be similar in thickness.
Add gel food coloring to each bowl, starting with a small amount and mixing thoroughly before adding more. The original cake uses pink, yellow, green, and blue. Scrape the sides and bottom of each bowl so you do not leave streaks of uncolored batter.
2. Fill the Pans and Bake
Prepare your pans according to the cake mix and pan instructions, then divide the colored batter among them. Spread the batter evenly without overfilling the pans. If you have more batter than your pans can accommodate, bake the remainder separately.
Use the oven temperature specified on the cake mix package. The shallow layers in my original class were approximately 1 inch thick, so I began checking them at the 15-minute mark. That is a first check, not a guaranteed baking time.
Check the center of each layer with a toothpick. It should come out without wet batter. The surface should also look set rather than wet or sunken.
3. Cool, Chill, and Check the Layers
Let the cakes cool enough to remove them from their pans without breaking, then finish cooling on a rack.
Once completely cool, wrap the layers and chill them until firm. Chilled layers are easier to handle and usually shed fewer crumbs as you frost them. Freezing is optional; the important checkpoint is that the layers feel firm enough to lift and stack.
Check the tops before assembly. If a layer has a dome, trim it so the next layer can sit evenly. My tutorial on how to torte and level a cake explains how to make a controlled, level cut.
4. Stack and Fill the Cake
Place a small dab of buttercream on the cake board to help hold the first layer in position. Center that layer on the board, then spread an even layer of buttercream over it.
Add the next cake layer and check the alignment before continuing. Repeat with the remaining layers, keeping the filling thickness consistent. Look at the stack from more than one side so you can correct a lean before coating the cake.
The filling should reach the edges without forming thick bulges between the layers.
5. Apply the Crumb Coat
Spread a thin layer of white buttercream over the top and sides. This first coat traps loose crumbs; it does not need to hide the colored layers completely.
Keep a separate bowl for buttercream scraped from the cake so crumbs do not get mixed into the clean frosting.
Chill the crumb-coated cake until the surface is firm enough that another coat will not drag it around. Some American buttercream recipes also form a surface crust, but the setting time depends on the recipe and room conditions.
6. Add the Final White Frosting Coat
Apply a fresh coat of white buttercream to the top and sides. Use an offset spatula to spread it, then smooth the sides with a scraper or the straight edge of your spatula.
Work with small adjustments. Fill low spots, scrape away excess frosting, and clean your tool between passes. Bring the frosting at the top edge gently toward the center to tidy the rim.
The white coating creates the background for the eyelashes and colorful mane. Aim for an even surface, but do not keep scraping once repeated passes stop improving it.
7. Prepare the Colored Buttercream
Divide your decorating buttercream among bowls and add your chosen gel colors. Fit the piping bags with star tips and compatible couplers if you want to change tips without changing bags.
The buttercream should be firm enough to hold the ridges from the star tip but soft enough to pipe without excessive pressure. Test a rosette on parchment paper. If its ridges disappear or it slumps, the buttercream is too soft. If the edges look torn and the frosting is difficult to squeeze, it may be too stiff.
Avoid overfilling the bags. You need enough room to close the top and control the pressure comfortably.
8. Position the Horn, Ears, and Eyelashes
Choose which side of the cake will face forward. Position the horn near the center of the top and place an ear on either side, following the topper manufacturer’s instructions.
Place the eyelashes on the front, checking their height and spacing before pressing them gently into the buttercream. Step back and look at the whole face before piping around it.
Use decorations intended for cake use, and remove nonedible toppers and their supports before slicing.
9. Pipe the Buttercream Mane
Hold the star tip approximately perpendicular to the surface where you are piping. Start with a small center, then move the tip in a tight circle around it while maintaining steady pressure. Stop squeezing before lifting the tip away.
Pipe clusters of rosettes around the horn and between the ears, bringing some of the mane toward the forehead. Alternate colors and tip sizes to create variation while keeping the eyelashes visible.
Fill small spaces with star dollops. To make a dollop, hold the tip in place, squeeze briefly, stop pressure, and lift away. These smaller shapes help connect the rosettes without crowding the design.
The star tips from the original class produce relatively small decorations. Rosette size will depend on the tip opening and how far you circle around the center.
10. Finish the Base and Add Sprinkles
Pipe a border around the bottom edge to connect the design and cover the seam where the cake meets the board. Use star dollops or small rosettes in the same colors as the mane.
Add optional sprinkles while the buttercream is still soft enough for them to adhere. Check the cake from the front and sides, then stop when the design looks balanced. Every space does not need another decoration.
Troubleshooting Your Unicorn Cake
| Problem | What to check | How to correct it |
|---|---|---|
| The stack leans | Uneven layers or filling | Level the layers and correct the filling before coating the cake |
| Crumbs appear in the final frosting | Crumb coat may not be set | Chill it until firm and use clean buttercream for the final coat |
| Rosettes lose their shape | Buttercream may be too warm or soft | Let it cool slightly, remix, and test the piping again |
| Piped edges look ragged | Buttercream may be too stiff, or the tip may be blocked | Check the tip and adjust the buttercream according to its recipe |
| Rosettes have long tails | Pressure continued while lifting | Stop squeezing before pulling the tip away |
| The face looks crowded | Mane is too close to the eyelashes | Keep a clear area around the eyes and build the mane mainly above them |
Frequently Asked Questions
Can I use a homemade cake instead of boxed mix?
Yes. Use a layer-cake recipe you trust and follow its pan, temperature, and baking instructions. The stacking and decorating method remains the same. Do not assume that every homemade recipe will tolerate added coloring or produce the same amount of batter.
Do I have to make rainbow layers?
No. The rainbow layers are part of this version, but the unicorn decorations work on an uncolored cake too.
Do I need all three star tips?
No. You can create the mane with one star tip and several buttercream colors. Multiple sizes give you more variety, but they are not required.
Why use couplers?
A compatible coupler lets you change piping tips while keeping the same bag of buttercream. Without one, fit the tip directly into the bag and keep that tip in place.
Can I use plastic piping tips?
Yes, if they produce the shape you want. Whether you can change them during decorating depends on their compatibility with your couplers.
How should I store the finished cake?
Follow the storage requirements of your cake, filling, and buttercream recipes. If refrigeration is required, place the cake in a covered cake box or carrier with enough clearance for the horn.
Allow serving time according to your frosting recipe so the buttercream has the intended texture. Remove nonedible decorations before cutting.
Practice the Piping Before Decorating the Cake
A few practice rosettes can tell you whether the buttercream is ready and help you find a comfortable piping rhythm. Once the layers are level, the coating is firm, and the piping holds its shape, you can focus on arranging the colors rather than correcting the cake underneath them.
How to make a Unicorn themed cake
Ingredients
Equipment
Method
- Bake, cool, and chill the layers before decorating. Trying to fill and frost a warm cake can soften the buttercream and pull crumbs from the layers.
- For a more manageable project, prepare the cake layers first and decorate them in a separate session. You can also practice the piping on parchment paper before working on the cake.
- Prepare and Color the Cake Batter
- Prepare the white cake mixes according to their package directions. Divide the batter evenly among four bowls so the finished layers will be similar in thickness.
- Add gel food coloring to each bowl, starting with a small amount and mixing thoroughly before adding more. The original cake uses pink, yellow, green, and blue. Scrape the sides and bottom of each bowl so you do not leave streaks of uncolored batter.
- Prepare your pans according to the cake mix and pan instructions, then divide the colored batter among them. Spread the batter evenly without overfilling the pans. If you have more batter than your pans can accommodate, bake the remainder separately.
- Use the oven temperature specified on the cake mix package. The shallow layers in my original class were approximately 1 inch thick, so I began checking them at the 15-minute mark. That is a first check, not a guaranteed baking time.
- Check the center of each layer with a toothpick. It should come out without wet batter. The surface should also look set rather than wet or sunken.
- Let the cakes cool enough to remove them from their pans without breaking, then finish cooling on a rack.
- Once completely cool, wrap the layers and chill them until firm. Chilled layers are easier to handle and usually shed fewer crumbs as you frost them. Freezing is optional; the important checkpoint is that the layers feel firm enough to lift and stack.
- Check the tops before assembly. If a layer has a dome, trim it so the next layer can sit evenly. My tutorial on how to torte and level a cake explains how to make a controlled, level cut.
- Place a small dab of buttercream on the cake board to help hold the first layer in position. Center that layer on the board, then spread an even layer of buttercream over it.
- Add the next cake layer and check the alignment before continuing. Repeat with the remaining layers, keeping the filling thickness consistent. Look at the stack from more than one side so you can correct a lean before coating the cake.
- The filling should reach the edges without forming thick bulges between the layers.
- Spread a thin layer of white buttercream over the top and sides. This first coat traps loose crumbs; it does not need to hide the colored layers completely.
- Keep a separate bowl for buttercream scraped from the cake so crumbs do not get mixed into the clean frosting.
- Chill the crumb-coated cake until the surface is firm enough that another coat will not drag it around. Some American buttercream recipes also form a surface crust, but the setting time depends on the recipe and room conditions.
- Apply a fresh coat of white buttercream to the top and sides. Use an offset spatula to spread it, then smooth the sides with a scraper or the straight edge of your spatula.
- Work with small adjustments. Fill low spots, scrape away excess frosting, and clean your tool between passes. Bring the frosting at the top edge gently toward the center to tidy the rim.
- The white coating creates the background for the eyelashes and colorful mane. Aim for an even surface, but do not keep scraping once repeated passes stop improving it.
- Divide your decorating buttercream among bowls and add your chosen gel colors. Fit the piping bags with star tips and compatible couplers if you want to change tips without changing bags.
- The buttercream should be firm enough to hold the ridges from the star tip but soft enough to pipe without excessive pressure. Test a rosette on parchment paper. If its ridges disappear or it slumps, the buttercream is too soft. If the edges look torn and the frosting is difficult to squeeze, it may be too stiff.
- Avoid overfilling the bags. You need enough room to close the top and control the pressure comfortably.
- Choose which side of the cake will face forward. Position the horn near the center of the top and place an ear on either side, following the topper manufacturer’s instructions.
- Place the eyelashes on the front, checking their height and spacing before pressing them gently into the buttercream. Step back and look at the whole face before piping around it.
- Use decorations intended for cake use, and remove nonedible toppers and their supports before slicing.
- Hold the star tip approximately perpendicular to the surface where you are piping. Start with a small center, then move the tip in a tight circle around it while maintaining steady pressure. Stop squeezing before lifting the tip away.
- Pipe clusters of rosettes around the horn and between the ears, bringing some of the mane toward the forehead. Alternate colors and tip sizes to create variation while keeping the eyelashes visible.
- Fill small spaces with star dollops. To make a dollop, hold the tip in place, squeeze briefly, stop pressure, and lift away. These smaller shapes help connect the rosettes without crowding the design.
- The star tips from the original class produce relatively small decorations. Rosette size will depend on the tip opening and how far you circle around the center.
- Pipe a border around the bottom edge to connect the design and cover the seam where the cake meets the board. Use star dollops or small rosettes in the same colors as the mane.
- Add optional sprinkles while the buttercream is still soft enough for them to adhere. Check the cake from the front and sides, then stop when the design looks balanced. Every space does not need another decoration.