Devil's Food Cake with Fudge Frosting

Ingredients

• 3/4 cup unsweetened cocoa powder, preferably Dutch-process
• 1 cup boiling strong coffee
• 1 3/4 cups all-purpose flour
• 1 1/2 teaspoons baking soda
• 1/2 teaspoon baking powder
• 1 teaspoon salt
• 1/2 cup unsalted butter, softened
• 1 3/4 cups packed dark brown sugar
• 3 large eggs
• 2 teaspoons vanilla extract
• 1/2 cup sour cream
• 1/2 cup unsalted butter
• 2/3 cup unsweetened cocoa powder
• 1/2 cup whole milk
• 4 cups powdered sugar
• 2 teaspoons vanilla extract
• 1/2 teaspoon salt

Before you cook

• Butter two 9-inch round cake pans and line the bottoms with parchment.
• Brew a cup of strong coffee and bring it to a boil.
• Set the eggs, butter, and sour cream out to come to room temperature.

Steps

1. Whisk the three-quarter cup of cocoa with the boiling coffee in a bowl until smooth and let it cool for 15 minutes.
2. Heat the oven to 350 degrees Fahrenheit.
3. Whisk the flour, baking soda, baking powder, and salt together.
4. Beat the half cup of butter with the brown sugar until fluffy, about 3 minutes.
5. Beat in the eggs one at a time, then the vanilla.
6. Whisk the sour cream into the cooled cocoa mixture.
7. Add the flour mixture to the butter in three additions, alternating with the cocoa mixture, mixing on low speed.
8. Divide the thin batter between the pans.
9. Bake for 30 to 35 minutes, until the cakes pull slightly from the sides and a toothpick comes out clean.
10. Cool the cakes in the pans for 15 minutes, then turn them out to cool completely on racks.
11. Melt the half cup of butter in a saucepan over medium heat.
12. Whisk in the two-thirds cup of cocoa and cook for one minute until it smells deeply chocolatey.
13. Whisk in the milk and bring it just to a simmer, then take the pan off the heat.
14. Beat in the powdered sugar a cup at a time until the frosting is glossy and thick.
15. Beat in the vanilla and salt, then let the frosting cool for 20 minutes to firm up.
16. Spread a third of the frosting over the first cake layer.
17. Set the second layer on top and cover the top and sides with the rest, working quickly before it sets.