Unicorn Cake

Bake the Cake Layers - Preheat the oven to 350°F. Lightly butter the bottom of three 6-inch cake pans and place a round of parchment on the bottom. If you don't have three pans, you will have to bake the layers in multiple rounds.

Bake the Cake Layers - Combine the dry ingredients: In a large bowl, whisk together the flour, baking powder, and salt, and set it aside.

Bake the Cake Layers - Whisk the eggs: In a mixing bowl with a spout, whisk together the eggs, egg white, and vanilla. Set it aside.

Bake the Cake Layers - Cream the butter and sugar: In a stand mixing bowl fitted with the paddle attachment, or in a large mixing bowl with a hand mixer, add the room temperature butter and sugar. Mix on medium speed for 4 to 5 minutes until it looks white in color and fluffy.

Bake the Cake Layers - Add the eggs and vanilla: With the mixer running on low, slowly stream in the whisked eggs and vanilla. Scrape down the bowl with a rubber spatula and mix one more time to ensure everything is well combined.

Bake the Cake Layers - Alternate dry and wet ingredients: Add a third of the dry ingredients to the mixing bowl and mix on low speed to combine. Then slowly stream in half of the buttermilk. Continue alternating dry and wet ingredients, ending on dry, until everything is combined.

Bake the Cake Layers - Add the sprinkles: Fold the sprinkles into the batter with a rubber spatula until just distributed to not overmix the batter.

Bake the Cake Layers - Distribute the batter: Evenly distribute the batter, about 2 cups (315g), into each of the prepared pans. Use a small offset spatula to evenly smooth the top of the batter to fill the pan.

Bake the Cake Layers - Bake: Bake the cakes for 25 to 26 minutes until the tops spring back when touched, or until a toothpick inserted into the center comes out clean with a few moist crumbs.

Bake the Cake Layers - Cool: Allow each pan to cool on a wire rack for 5 minutes, then turn over each pan and remove the cake. They should fall right out with no resistance. Let the cake layers cool completely on a wire rack.

Make the Buttercream - Beat the butter, then add the powdered sugar: In a stand mixing bowl fitted with the paddle attachment, or in a large mixing bowl with a hand mixer, beat the butter on medium speed until smooth, about 2 minutes. Add the powdered sugar. Mix on low speed until combined, then increase the speed to medium-high and continue mixing until white and fluffy, 3 to 4 minutes.

Make the Buttercream - Add the milk and vanilla: Add the milk and vanilla and mix on low speed until combined. Then increase the speed to medium and mix again until fluffy, about 30 seconds. Set aside about 2 1/2 cups of the frosting in a medium bowl and cover with plastic wrap. This frosting will be used for decorating the unicorn cake.

Assemble the Cake and Components - Layer the cakes with frosting: Place one cake layer right side up on a large plate or cardboard cake round at least 2 inches larger than the cake. Use an offset spatula or butter knife to spread about 1/2 cup of the frosting evenly over the layer. Add the next layer and spread another layer of frosting, about 1/2 cup. Place the last cake layer up-side-down, so the top of the cake is smooth and flat. Make sure that the cake layers are centered, and the top of the cake is level.

Assemble the Cake and Components - Apply the crumb coat: Spread a thin layer of frosting, about 1/2 to 2/3 cup over the top and sides of the cake using an offset spatula or the straight edge of a large butter knife. Use the spatula to spread the frosting into a thin, even layer. You should be able to see the cake through the frosting. This thin layer of frosting is called the crumb coat and helps catch any loose crumbs on the outside of the cake so that the final layer of frosting doesn't have any crumbs caught in it.

Assemble the Cake and Components - Chill the cake: Place the cake, uncovered, in the freezer or fridge for 10 to 15 minutes until the frosting is set.

Assemble the Cake and Components - Frost the cake: Spread a generous amount of frosting (about 2 cups) over the top and sides of the cake, this time leaving a thicker layer of frosting. Use the offset spatula or the back of a butter knife to smooth the sides.

Assemble the Cake and Components - Make the horn and ears: Keep 1 sugar cone whole. Use a serrated knife to gently cut the other 2 sugar cones roughly in half horizontally to shorten the cones to about 2 1/2 inches—the pointed ends will be the ears. Place the two cone ears and the full cone horn in a plastic bag or box. Spray the cones generously with the gold spray. Turn them with your hands as needed and continue spraying until they are completely coated. Set them aside on a paper towel standing up to dry.

Decorate the Cake - Color the buttercream: In a small bowl, add about 1 tablespoon of the buttercream. Add in 3 to 4 drops of black food coloring and stir to combine. This will be for the eyes. Set the bowl aside and cover with plastic wrap to keep from drying out. In 5 small bowls, add about 1/2 cup of buttercream to each bowl (from the 2 1/2 cups you reserved for decorating). Add a very small drop of yellow, pink, green, blue, and purple to each bowl and stir to combine.

Decorate the Cake - Fill the piping bags: In a small 12-inch piping bag fitted with a small round tip, add the black colored buttercream and set it aside. In a large 2-inch piping bag, cut the tip and fit it with a large star piping tip. Grab 5 (18-inch) disposable piping bags. Fill each bag with one of the colored bowls of buttercream. Use the dull edge of a butter knife or plastic scraper to scrape the buttercream down towards the tips of the bags to remove any excess air and flatten it in the bag.

Decorate the Cake - Create the rainbow piping bag: Cut about 1/2 inch off the tip of each bag with the colored frosting. Stack the piping bags on top of each other and then place them inside the large piping bag. Twist the top of the bag and then gently squeeze to push the buttercream down to the tip.

Decorate the Cake - Assemble the horn and ears: Gently stick the large ice cream cone into the center of the top of the cake to secure it. Then place the two small cones on either side of the horn.

Decorate the Cake - Pipe the mane: Use the colored piping bags to pipe various sized rosettes and dollops on the top of the cake, on both sides of the cones, and in between the cones to fill in any empty space. Then working down the backside of the cake, pipe more rosettes and dollops of buttercream over the entire back, moving slightly towards one side to make it look like the mane of the unicorn is flowing around the side. Finally, turn the cake around and pipe a few more on the top edge of the cake down 1 inch of the front.

Decorate the Cake - Pipe the face: After the mane is finished, use the piping bag filled with black buttercream to create two half-moon lines about one inch apart in the very center of the cake underneath the tip of the buttercream mane. Pipe six lines on top of each moon for the eyelashes.

Decorate the Cake - Serve: Once the cake is assembled and decorated, it's best to store it in the fridge until you are ready to eat it. I recommend pulling the whole cake out a few hours before cutting and serving to allow the cake to come back to room temperature which makes it easier to cut.