Some good recipes.
Triple Chocolate Peanut Butter Layer Cake
Source: This here is some mad scientist stuff. Recipes I borrowed from are listed below.
Servings: Makes a 10 inch cake (or a 9 inch with some extra cupcakes).
Prep Time: 2 hoursCook Time: 1 hour
Peanut Butter Buttercream Frosting
Chocolate Peanut Butter Ganache Frosting
To make the cake layers:
Preheat oven to 300°F. Lightly grease either 9 or 10 inch round cake pans and then line the bottoms with discs of parchment.
Finely chop the chocolate and in a bowl combine with hot coffee, salt and vanilla. Let mixture stand, stirring occasionally, until chocolate is melted and mixture is smooth. Then into a large bowl whisk together flour, cocoa powder, baking soda, and baking powder.
In the bowl of a stand mixer, beat eggs and oil together for about 3 minutes at medium speed. Slowly add buttermilk and melted chocolate/coffee mixture to the eggs, on medium-low speed until integrated. Continuing on medium-low, slowly add sugar and then slowly add the flour and cocoa mixture until just combined. Divide batter between pans; about 2.4 oz for a 9 inch and about 2.8 oz each for a 10 inch pan. Bake on the center rack for 60 to 70 minutes or until a bamboo skewer comes out clean (If you're using 9 inch pans, then you'll also get about 5 cupcakes out of that surplus batter).
Cool layers completely in their pans resting on racks. Run a knife around edges of the cakes to loosen 'em up (find a plastic knife if you're rocking nonstick) and invert layers onto wire racks. Carefully remove parchment and wrap each layer completely in plastic wrap to freeze for at least eight hours.
To make the Peanut Butter Buttercream:
Mix peanut butter, butter, salt, rum, and milk (all but the powdered sugar) together with the whisk attachment in the stand mixer on medium-high for 3 minutes. Slowly add powdered sugar until your desired consistency is reached. If the frosting starts to dry out and "ball up" as the sugar is added then you can adjust the consistency as needed with milk added by the tablespoon.
To make the Ganache Frosting:
Combine cream and vanilla in a small saucepan and bring to a simmer over medium heat. Into the bowl of a stand mixer with your whisk attachment, add chocolate chips, peanut butter and corn syrup. Pour the hot cream over chocolate mixture and let sit until chocolate is mostly melted; about two minutes. Whip it all up on medium speed until the ganache begins to cool and just starts to become lighter and spreadable. If it all gets too cold and sets up, then move the mess to a microwave-safe container and nuke and stir until it just becomes spreadable again.
To assemble the cake:
Pull the layers from the freezer and level with a large serrated knife (if needed). Move the bottom layer to a parchment or foil-covered surface (such as a cardboard disk), and pipe or spread the peanut butter buttercream on the top (lay it on thick). Place the top cake layer and fill in any between-layer voids with more buttercream. Next, frost the whole cake with the chocolate peanut butter ganache using an offset spatula. Dip the spatula in hot water as needed to smooth the ganache and keep stickage to a minimum. Move quick, as the ganache will want to set up on those cold cake layers! To finish, pipe the edges and top with any additional buttercream and/or ganache you have (you'll have significant surplus on a 9 inch cake; the 10 inch variant will be just about right). Garnish with peanut butter cups (because you can).
To make the cake layers:
That total prep and bake time is really a guess. I put down three hours total because it took me four. I might be the slowest cake decorator ever.