Step 1

Preheat oven to 350°F (177°C). Grease three 9-inch cake pans, line with parchment paper rounds, then grease the parchment paper. Parchment paper helps the cakes seamlessly release from the pans. (If it’s helpful, see this parchment paper rounds for cakes video & post.)

Step 2

Whisk the flour, cocoa powder, sugar, baking soda, baking powder, salt, and espresso powder (if using) together in a large bowl. Set aside. Using a handheld or stand mixer fitted with a whisk attachment (or you can use a whisk), mix the oil, eggs, and sour cream together on medium-high speed until combined. Add the buttermilk and vanilla and beat until combined. Pour the wet ingredients into the dry ingredients, add the hot water/coffee, and whisk or beat on low speed until the batter is completely combined. Fold in the flour-coated chocolate chips. Batter is thin and you may see some air bubbles on the surface—that’s normal. You should have about 6–6.5 cups of batter, or around 1400g.

Step 3

Divide batter evenly between 3 pans. Bake for approximately 24–26 minutes. Baking times vary, so keep an eye on yours. The cakes are done when a toothpick inserted in the center comes out clean.

Step 4

Remove the cakes from the oven and set on a wire rack. Allow to cool completely in the pan. The cakes may slightly sink in the middle as they cool—that’s expected.

Step 5

With a handheld or stand mixer fitted with a paddle attachment, beat the butter on medium high speed until creamy and smooth, about 2 minutes. With a rubber spatula, scrape down the sides and bottom of the bowl as needed. Add the peanut butter and beat until completely combined, about 1–2 minutes. Scrape down the sides and bottom of the bowl as needed to help combine. Mixture will be thin. Add confectioners’ sugar, vanilla extract, and salt and then pour in the heavy cream with the mixer running on low speed. After all of the cream has been added, turn the mixer up to medium-high speed and beat for 1–2 minutes, or until fully combined and creamy. Add up to 1/4 cup more confectioners’ sugar if frosting seems quite thin. You should end up with about 3.5–4 cups (850g) of peanut butter frosting. This amount makes enough for the filling, crumb coat, and for a little piping on top.

Step 6

Place 1 cake layer on your cake stand, cake turntable, or serving plate. Using a large icing spatula or small offset spatula, evenly cover the top with about 1 cup peanut butter frosting. Repeat with 2nd and 3rd cake layers, spreading about 1 cup of peanut butter frosting in between each layer. Spread a thin layer of frosting on the top and around the sides as a crumb coat. Run a bench scraper around the cake to smooth out crumb coat. Chill uncovered in the refrigerator for at least 30 minutes and up to 3 hours to set the crumb coat.

Step 7

Place finely chopped chocolate in a medium heat-proof bowl. Heat the cream in a small saucepan over medium heat until it begins to gently simmer. (Do not let it come to a rapid boil—that’s too hot!) Pour over chocolate, then let it sit for 2–3 minutes to gently soften the chocolate. With a metal spoon or small rubber spatula, very slowly stir until chocolate has melted and mixture is smooth. Ganache is thin. The finer you chopped the chocolate, the quicker it will melt with the cream. If it’s not melting, do not microwave it. If needed, see Troubleshooting Chocolate Ganache. Once ganache mixture is smooth, let it chill for 20-30 minutes in the refrigerator to thicken before spreading on chilled crumb-coated cake.

Step 8

Pour/spoon thickened ganache on chilled cake. Smooth the top with an icing spatula and the sides with a bench scraper. If desired, pipe remaining peanut butter frosting around the edge of the cake. I used Wilton 1M piping tip on the pictured cake. Garnish with peanut butter cups, if desired. Serve cake immediately or chill, uncovered, for up to 4–6 hours before serving. Cake can be served at room temperature or chilled.

Step 9

Cover leftover cake tightly and store in the refrigerator for 5 days. I like using a cake carrier for storing and transporting.