Preheat oven to 375F. Lightly grease and flour two 8" round pans. Combine Basic Cake Mix and cocoa in a large bowl. Add 1/2 cup of the milk and beat at medium speed for 2 minutes. Add Remaining 1/2 cup milk, eggs, and melted butter. Beat 2 more minutes. Pour into prepared pans. Bake 25 to 30 minutes, till a toothpick inserted in center comes out clean. Cool in pans 10 minutes, then cool on wire racks. Frost as desired.