Sour Cream-Fudge Layer Cake with Chocolate Butter Icing

NOTE: Sour cream gives this cake its smooth, rich chocolate flavor and dense yet melting texture, almost like fudge. An equally intense chocolate icing stands up to the rich cake. It's best not to refrigerate this cake, but if you do, cut it while cold, then let the slices come to room temperature before serving.

INSTRUCTIONS:

1. Follow master recipe for Basic Chocolate Cake, making the following changes: Use two 9-by-1¹/₂-inch or -2-inch round cake pans. Increase cocoa to 1 cup. Whisk ¹/₂ cup sour cream into cocoa mixture along with vanilla. Increase butter to 1 cup (2 sticks), sugar to 1³/₄ cups, and baking soda to ³/₄ teaspoon.

2. When layers are cool, frost cake.