Yield: 1 (9-inch) 3-layer cake

1 cup unsalted butter, softened
2½ cups sugar
6 large eggs, at room temperature
2¾ cups cake flour
¼ cup unsweetened natural cocoa powder
¾ teaspoon salt
¼ teaspoon baking soda
1 (8-ounce) container sour cream, at room temperature
½ cup whole buttermilk, at room temperature
2 (1-ounce) bottles red food coloring
1 1/2 teaspoons vanilla extract
1 recipe Peppermint Mousse Filling
1 recipe Peppermint Creme Icing
Garnish: crushed soft peppermints
1. Preheat oven to 350°. Spray 3 (9-inch) round cake pans with baking spray with flour; line with parchment rounds, and spray again. Set aside.

2. In a large bowl, beat butter and sugar at high speed with an electric mixer until light and fluffy. Add eggs, one at a time, beating well after each addition.

3. In a medium bowl, whisk together flour, cocoa powder, salt, and baking soda. Set aside. In a small bowl, combine sour cream, buttermilk, red food coloring, and vanilla. Add flour mixture to butter mixture, alternately with sour cream mixture, beginning and ending with flour mixture. Divide batter evenly among prepared pans.

4. Bake until a wooden pick inserted in the center comes out clean, approximately 30 minutes. Let cool in pans for 10 minutes. Remove from pans, and let cool completely on wire racks.

5. Trim layers, if necessary, to make them flat. Spread Peppermint Mousse Filling in between layers. Spread sides and top of cake with Peppermint Crème Icing. Garnish sides and top of cake with crushed soft peppermints, if desired. Store in refrigerator.