Preheat the oven: Begin by preheating your oven to 350°F (175°C). Line two cupcake tins with liners and set aside.

Prepare the dry ingredients: In a medium bowl, whisk together the cake flour (or all-purpose flour and cornstarch), baking powder, and salt until well combined.

Mix the wet ingredients: In the bowl of a stand mixer fitted with a paddle attachment, beat the softened butter and vegetable oil together until smooth, about 3 minutes. Gradually add the granulated sugar, beating on high until the mixture is light and fluffy, about 3 minutes more.

Incorporate the eggs and vanilla: Add the eggs one at a time, mixing well after each addition. Stir in the vanilla bean paste or vanilla extract until fully incorporated.

Combine dry and wet ingredients: Gradually add half of the dry ingredients to the wet ingredients, followed by the buttermilk. Repeat until all ingredients are incorporated and the batter is fluffy.

Fill the cupcake liners: Using a cookie scoop, portion the batter into the prepared cupcake liners, filling each no more than 3/4 full.

Bake to perfection: Bake the cupcakes for 18-20 minutes, or until a toothpick inserted into the center comes out mostly clean. Allow the cupcakes to cool completely before frosting.

Frost and serve: Once cooled, frost the cupcakes using a piping bag fitted with a large star tip (1M) for an elegant finish.