Chocolate Birthday Cake

Preparation

1. Step 1

   Make the cake: Grease three 8-inch round cake pans using a paper towel dabbed with a generous amount of olive oil. Line the bottoms with rounds of parchment paper. Position racks in the top and bottom thirds of the oven and heat oven to 350 degrees.

2. Step 2

   In a large bowl, whisk the cocoa powder and hot coffee until smooth. Add the chocolate and stir occasionally until fully melted and mostly cooled, about 1 minute. Vigorously whisk in the extra-virgin olive oil until smooth. Add the sugar and whisk until smooth, then add the eggs, sour cream and vanilla, breaking each yolk before whisking until very smooth.

3. Step 3

   Sift in the flour, baking powder, baking soda and salt. (If you don’t have a sieve, you can whisk these dry ingredients in a separate bowl, then add to the wet ingredients.) Whisk just until incorporated and no flour streaks remain. The batter will be thin.

4. Step 4

   Divide the batter evenly among the three prepared pans (about 390 grams per pan). Place two of the pans on the top rack and one on the bottom. Bake, swapping the position of the bottom cake with the top two halfway through, until the cakes pull away from the sides of the pans, the tops are cracking slightly and a toothpick inserted in the centers comes out clean, 25 to 30 minutes.

5. Step 5

   Let the cakes cool completely, then remove from the pans to frost right away or wrap in plastic wrap or foil and freeze for up to 3 days. (To help the cakes release from the pans, run a dull, slightly flexible knife or offset spatula around the edges and slightly underneath the cakes.)

6. Step 6

   While the cakes bake and cool, make the frosting: In a medium saucepan, whisk the sugar, flour and salt. Whisk in the milk until smooth. Cook over medium heat, whisking constantly, until the mixture starts to bubble, about 4 minutes, then continue whisking the boiling mixture until it’s thick like pudding, about 2 minutes longer. Transfer to the bowl of a stand mixer fitted with the paddle attachment.

7. Step 7

   Beat on high speed until the bowl feels cool to the touch. It may take up to 5 minutes. With the mixer on medium-high speed, add the butter 2 tablespoons at a time, beating until smooth between additions. When all of the butter has been incorporated, raise the speed to high and beat until white and very fluffy, 3 to 5 minutes. Stop the mixer, add the sour cream and vanilla, then beat on low just until incorporated.

8. Step 8

   Frost the cake: Place one cake layer bottom-side up on a flat plate or cake stand, then top with about ¾ cup of the frosting and spread evenly using an offset spatula. Don’t worry about the sides yet. Repeat with the second and third cake layers, placing them bottom-sides up. With the remaining frosting, frost the sides of the cake. It’s okay if you don’t cover the sides completely like the inner layers, but do make sure there are no gaps at the edges where the layers meet. Refrigerate until firm and set, then serve cold or bring to room temperature first if you prefer. The cold, set cake can be wrapped in plastic and refrigerated for up to 24 hours or frozen for up to a month. Thaw before serving if needed.