Rich Chocolate Cake
Preheat oven to 350 degrees. Coat cake pans with cooking spray. Line bottoms with parchment paper; coat with cooking spray. Dust pans with cocoa, tapping out excess.Advertisement
Sift cocoa, flour, sugar, baking soda, baking powder, and salt into the bowl of a mixer fitted with the paddle. Add eggs, egg yolk, warm water, milk, oil, and vanilla; beat on low speed until smooth and combined, about 3 minutes.
Divide batter among lined pans. Bake until a cake tester inserted into centers comes out clean, about 35 minutes for 9-inch pan (longer for larger sizes). Let cool in pans on wire racks 25 minutes. Turn cakes out onto racks, remove parchment, and re-invert cakes so they are right side up; let cool completely.
Batter amounts for each 3-inch-deep pan (fills pans halfway): 20-inch, 24 cups; 18-inch, 21 cups; 14-inch, 15 cups; 9-inch, 7 cups; 6-inch, 3 cups