Chocolate Lover'S Chocolate Cake
["1 (2 layer size) pkg. chocolate cake mix (not pudding in the mix variety)", "1/2 c. unsweetened cocoa", "3 eggs", "1 1/3 c. water", "1 c. mayonnaise"]
["Heat oven to 350\u00b0.", "Grease and flour two (9-inch) round cake pans.", "Line bottom of pans with wax paper."]
["layer", "unsweetened cocoa", "eggs", "water", "mayonnaise"]