Moist Devil's Food Cake with Mrs. Milman's Chocolate Frosting

Preheat oven to 350 degrees. Butter three 8-inch round cake pans. Line bottoms with parchment; butter parchment. Dust with cocoa powder; tap out excess. Set aside. Sift cocoa powder into a medium bowl; whisk in boiling water. Set aside to cool.

Sift together flour, baking soda, and salt into a large bowl; set aside. Put butter into the bowl of an electric mixer fitted with the paddle attachment. Mix on low speed until creamy. Gradually mix in sugar until pale and fluffy, 3 to 4 minutes. Add eggs, a bit at a time, mixing well between each addition; mix until well blended. Mix in vanilla.

Whisk milk into reserved cocoa mixture. With mixer on low speed, add flour mixture to butter mixture in 3 batches, alternating with the cocoa mixture.

Divide batter evenly among prepared pans; smooth tops with an offset spatula. Bake, rotating pans halfway through, until a cake tester inserted into centers comes out clean, 35 to 45 minutes. Let cool in pans on wire racks 15 minutes. Turn our cakes onto racks; remove parchment, and reinvert. Let cool completely.

Place 1 cake layer on a serving platter or cake stand. Spread 1 1/2 cups frosting over top. Add second cake layer, and spread 1 1/2 cups frosting over top. Top with third cake layer. Spread remaining 3 cups frosting over top and sides of assembled cake. Cake can be covered with a cake dome or plastic wrap, and stored at room temperature up to 3 days.