Secret-Ingredient Dark Chocolate Cake

Step 1
Preheat the oven to 325 degrees F (165 degrees C). Grease three 8-inch round cake pans and line bottoms with parchment paper.

Step 2
Sift flour, cocoa powder, baking soda, salt, and baking powder into a large bowl.

Step 3
Combine stout, vanilla extract, and espresso powder in separate bowl and stir.

Step 4
Beat sugar and butter together in another bowl until creamy, scraping sides occasionally. Add eggs, one at a time, mixing after each addition. Beat in mayonnaise. Alternate adding the flour and stout mixtures, 1/3 at a time, beating after each addition. Fold in dark chocolate just until combined. Split batter between the 3 prepared pans and level out the tops.

Step 5
Bake in the preheated oven until a toothpick inserted into the cakes comes out clean, about 35 minutes. Cool in the pans for 15 minutes, then run a knife around the edge and flip onto a cooling rack. Let cool completely.