Preheat your oven to 350°F (or 177°C). Grease and line three 6x2 pans with some parchment paper.

Whisk together flour, sugar, cocoa powder, baking powder, baking soda, salt, and optional espresso powder.

Beat oil, sour cream, and eggs with your mixer at medium speed, then add vanilla and buttermilk and beat again. Combine wet and dry ingredients, add hot coffee or water, and mix until smooth at low speed.

Fold in flour-covered chocolate chips. The smooth batter should yield about 4 to 4 ⅓ cups.

Divide batter into pans and bake for 24 to 26 minutes until a small toothpick comes out mostly clean.

Cool your baked cakes on wire racks.

Beat butter until creamy, then mix in peanut butter. Add confectioners' sugar, vanilla, and salt, then slowly pour in heavy cream. Beat until combined (1 to 2 minutes).

Adjust frosting consistency with more confectioners' sugar (2 ⅔ tablespoons) if needed. That should yield around 2 ½ to 2 ⅔ cups of frosting.

Spread frosting between cake layers.

Spread a layer of frosting around the cake's sides and top. Chill the cake (uncovered) for 30 mins to 3 hours.

Fill a bowl with chopped chocolate. Heat cream until warm but not boiling. Pour over the chocolate and let it soften, then stir until smooth. Let it sit in the fridge for 30 minutes to thicken.

Spread and smooth the ganache over your chilled crumb-coated cake. Optionally, pipe extra frosting on the edges and use peanut butter cups as garnish.

Serve immediately, or let your frosted cake chill in the fridge for 4 to 6 hours (uncovered) before serving.