Step 1

Place a rack in the middle of the oven and preheat to 350 degrees F.

Step 2

Coat two 9 inch round cake pans with butter and place a parchment circle in the bottom of each. Coat the parchment with more butter then coat the inside each buttered pan with a dusting of cocoa powder.

Step 3

Add the flour, sugar, cocoa powder, baking powder, baking soda, and salt to a large bowl and whisk to combine. Place the buttermilk, vegetable oil, eggs, and vanilla extract in a separate bowl and whisk to combine. Add the buttermilk mixture to flour mixture, then stir with a rubber spatula until smooth. Add the hot coffee and stir until completely smooth. The batter will be very thin. Transfer the batter to the prepared pans and smooth each out into an even layer.

Step 4

Bake until a toothpick inserted in the center of the cake comes out clean, 25 to 30 minutes. Transfer the pans to a wire rack and let cool completely, for at least 1 hour.

Step 5

Add butter and peanut butter to the bowl of a stand mixer fitted with a paddle attachment and beat until creamy and well-combined.

Step 6

With mixer on low speed, gradually add powdered sugar (about 1/3 cup at a time) until completely combined. Be sure to scrape the sides and bottom of the bowl so all ingredients are well incorporated.

Step 7

Stir in vanilla extract and salt.

Step 8

With mixer on low-speed, add milk and mix until well-combined. Gradually increase speed to high and beat for 30 seconds.

Step 9

Once cakes are cooled, remove them from the pans and discard the parchment paper. Trim the top of each so they are flat. Place a dollop of frosting on the bottom of your cake plate or cardboard cake round (to help secure cake) and flip one cake over and gently transfer it to the cake plate on top of frosting. The bottom of the cake should now be on top.

Step 10

Generously coat the top of the cake with frosting then add second cake layer with the bottom facing up. Coat the outside of the cake with a very thin crumb coat and refrigerate for at least an hour to set the crumb coat.

Step 11

Once crumb coat is set, frost the cake evenly with the remainder of the frosting. To create a swoopy finish, use the back of an offset spatula or spoon to gently press down as you swoop frosting in an "S" motion, pulling spatula or spoon away quickly to create little "peaks". Add espresso or chocolate chips to the bottom of the cake by gently pressing them into the sides by hand.