FOR THE VANILLA FROSTING
2 teaspoons vanilla extract
1-2 tablespoons heavy cream
2 cups (450 grams, 4 sticks) unsalted butter, at room temperature
5 cups (575 grams) confectioner’s sugar
Pinch of salt
Purple gel paste food coloring
FOR THE FROSTING
Using an electric mixer, beat the butter on medium speed until pale and creamy (2-3 minutes).
Add the powdered sugar and salt and beat over low heat until just combined. Turn over medium heat and beat for 2-3 more minutes.
Add the vanilla extract and beat to combine.
Add the cream 1 tablespoon at a time until you reach the desired consistency.
TO ASSEMBLE THE CAKE
Place the white cake layer on a 6-inch cake board. Spoon about 1/2 cup frosting on top and spread evenly with a spatula. Place the next layer on top of the first and repeat the process with the next 4 layers.
Scoop a generous dollop of frosting on top of cake and spread evenly across top of cake. Work down the sides until the entire cake is covered in a thin layer of frosting.
Let the crumb layer rest in the fridge for about 30 minutes.
Once the crumb coat has set, spread a thicker layer of frosting on the top and sides of the crumb coat to create a smooth finish.
Divide the leftover frosting into 3 bowls and tint each with food coloring.
Spoon the frosting into 3 separate piping bags fitted with star tips to decorate the top of the cake.