Ingredients:

  • 3 cups cake flour, sifted
  • 3.5 cups granulated sugar, divided
  • 4 cups unsalted butter (907g), softened and divided
  • 1 cup whole milk, room temperature
  • 12 large egg whites, room temperature and divided
  • 2 teaspoons baking powder
  • 1 teaspoon fine sea salt, divided
  • 1 tablespoon pure vanilla extract, divided
  • Assorted gel food coloring (pink, blue, purple, yellow)
  • Edible gold dust
  • Unicorn horn and ear toppers (kit)

Instructions:

  1. Preheat oven to 350°F (175°C). Grease and flour four 6-inch cake pans. Using the Reverse Creaming Method, combine sifted cake flour, 1.5 cups sugar, baking powder, and 1/2 tsp salt. Add 1 cup of softened butter and mix on low until crumbly. Gradually stream in the milk and 6 egg whites until just combined. Fold in 1 tsp vanilla. Divide batter evenly among pans and bake for 25-30 minutes, or until a toothpick comes out clean. Cool completely on wire racks.
  2. Combine remaining 6 large egg whites and 2 cups sugar in a heatproof bowl set over a saucepan of simmering water (double boiler). Whisk constantly until the sugar dissolves completely and the mixture reaches 160°F (71°C). Transfer to a stand mixer bowl and whip on high speed until stiff, glossy peaks form and the bowl is cool to the touch (about 10-15 minutes). Reduce speed to medium-low and add the remaining 3 cups of softened butter, piece by piece, until fully emulsified. Increase speed to medium-high and whip until fluffy and smooth. Add remaining salt and vanilla.
  3. Level the cooled cake layers. Stack the layers, filling generously with SMBC. Apply a thin layer of buttercream (the crumb coat) over the entire cake. Chill the cake in the refrigerator for at least 30 minutes until firm—this step is non-negotiable for structural success.
  4. Apply a thick, even final coat of white SMBC to the entire cake. Divide the remaining buttercream into small bowls and color them with assorted pastel food gels (pink, blue, purple, etc.) for the mane.
  5. Using piping bags fitted with star tips, pipe colorful swirls and rosettes along the top edge of the cake to create the unicorn's mane. Dust the included horn and ears with edible gold dust and gently insert them into the top center of the cake. Chill the finished cake for at least 30 minutes before serving.