• Preheat your oven to 350°F (177°C). Grease three 9-inch round cake pans, then line the bottoms with parchment paper rounds and grease the parchment as well. This step ensures the cakes release easily after baking. (If needed, you can refer to a video or tutorial on how to cut parchment rounds for cakes.)

Make the Cake:

• In a large mixing bowl, whisk together the flour, cocoa powder, sugar, baking soda, baking powder, salt, and espresso powder (if using). Set the dry ingredients aside. In a separate bowl, using a handheld mixer or a stand mixer fitted with a whisk attachment (or simply a hand whisk), mix the oil, eggs, and sour cream on medium-high speed until well combined. Add the buttermilk and vanilla extract, and continue beating until fully incorporated. Slowly pour the wet ingredients into the dry ingredients, then add the hot water or coffee. Mix on low speed or gently whisk by hand until the batter is smooth and fully combined. Fold in the mini chocolate chips that have been tossed in flour. The batter will be thin and may have some air bubbles on the surface, which is completely normal. You should have about 6 to 6½ cups of batter (approximately 1400g).
• Divide the batter evenly among the prepared cake pans. Bake for 24 to 26 minutes, or until a toothpick inserted in the center of each cake comes out clean. Baking times may vary, so it’s a good idea to check a few minutes early.
• Once baked, remove the cakes from the oven and place them on a wire rack to cool completely in the pans. It's normal for the centers to sink slightly as they cool.

Make the Peanut Butter Frosting:

• While the cakes are cooling, prepare the frosting. Using a stand or hand mixer fitted with a paddle attachment, beat the softened butter on medium-high speed until smooth and creamy, about 2 minutes. Scrape down the sides and bottom of the bowl with a rubber spatula as needed. Add the creamy peanut butter and continue beating for another 1–2 minutes, until the mixture is fully blended. Again, scrape the sides and bottom to ensure everything is well combined. The mixture may seem thin at this point. Add the confectioners’ sugar, vanilla extract, and salt. With the mixer on low speed, slowly pour in the heavy cream. Once all the cream is added, increase the mixer speed to medium-high and beat for 1–2 minutes until the frosting is creamy and well combined. If the consistency is too thin, you can add up to ¼ cup more confectioners’ sugar. This recipe yields about 3½ to 4 cups (approximately 850g) of frosting—enough for filling, a crumb coat, and some decorative piping.

Assemble the Cake + Apply a Crumb Coat:

• Place the first cake layer on a cake stand, turntable, or serving plate. Spread about 1 cup of peanut butter frosting evenly across the top. Repeat this process with the second and third layers, adding about 1 cup of frosting between each. Apply a thin layer of frosting around the entire cake to act as a crumb coat, smoothing it with a bench scraper or spatula. Refrigerate the cake, uncovered, for at least 30 minutes (or up to 3 hours) to allow the crumb coat to set.

Make the Chocolate Ganache:

• While the cake chills, prepare the ganache. Place the finely chopped chocolate into a medium heatproof bowl. In a small saucepan, heat the cream over medium heat until it gently simmers—do not let it come to a full boil. Pour the hot cream over the chocolate and let it sit undisturbed for 2–3 minutes to soften the chocolate. Then, using a metal spoon or small rubber spatula, gently stir until the chocolate is fully melted and the mixture is silky smooth. The ganache will be thin at first; this is normal. The finer the chocolate is chopped, the quicker and more evenly it will melt. If needed, chill the ganache in the refrigerator for 20–30 minutes to allow it to thicken to a spreadable consistency. (Avoid using the microwave to reheat.)
• Once the ganache has thickened, pour or spoon it over the chilled, crumb-coated cake. Use an offset spatula to smooth the top and a bench scraper for the sides. If desired, pipe remaining peanut butter frosting around the top edge of the cake using a decorative piping tip—Wilton 1M was used in the original version. Garnish with chopped or mini peanut butter cups for extra flair.
• Serve the cake immediately, or refrigerate uncovered for up to 4–6 hours before serving. It can be served either chilled or at room temperature.

Storage:

• Cover any leftover cake tightly and refrigerate for up to 5 days. A cake carrier works well for both storing and transporting the cake.