Cotton Candy Cake

Name: Cotton Candy Cake
Cuisine: European
Ingredients: 1 whole egg (I use extra large, at room temperature); 3 egg whites (also extra large, at room temperature); 1 cup 240 g buttermilk, room temperature; 1 tablespoon 13 g Lorann Cotton Candy Flavoring; 3 cups (plus 2 tablespoons (366.6 g) cake flour); 1 3/4 cups 350 g granulated sugar; 1 tablespoon plus 1 teaspoon (16 g baking powder); 3/4 teaspoon 4.2 g salt; 1 cup 226 g unsalted butter, room temperature; Pink and blue food gel (optional); 2 cups 452 g unsalted butter, slightly chilled; 6 cups 750 g powdered sugar, measured then sifted; 3 tablespoons 43.3 g heavy cream; 2 teaspoons 8 g Lorann Cotton Candy Flavoring; Pinch of salt; Cosmic Rush Twinkle Sprinkle Medley; *This buttercream recipe makes enough to fill and cover your cake. If you want to add additional piping