Preheat oven to 350°F (177°C). Grease three 9-inch cake pans, line with parchment paper rounds, then grease the parchment paper.

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, 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.

Divide batter evenly between 3 pans. Bake for 24–26 minutes or until a toothpick inserted in the center comes out clean.

Cool the cakes in the pans set on a cooling rack for 1 hour. Run a knife around the edges to help loosen the sides, remove the cakes from the pans, peel off the parchment, and place on the rack to finish cooling.

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. Add the peanut butter and beat until completely combined.

Add confectioners’ sugar, vanilla extract, and salt and then pour in the heavy cream with the mixer running on low speed. Beat for 1–2 minutes, or until fully combined and creamy.

Place 1 cake layer on your cake stand. Cover the top with about 1 cup of peanut butter frosting. Repeat with 2nd and 3rd cake layers.

Spread a thin layer of frosting on the top and around the sides as a crumb coat. Chill uncovered in the refrigerator for at least 30 minutes.

Make the chocolate ganache: Place finely chopped chocolate in a medium heat-proof bowl. Heat the cream in a small saucepan until it begins to gently simmer. Pour over chocolate, then let it sit for 2–3 minutes to gently soften the chocolate.

Stir until chocolate has melted and mixture is smooth. Refrigerate for at least 30 minutes to thicken before spreading on the crumb-coated cake.

Pour/spoon thickened ganache on chilled cake. Smooth the top with an icing spatula and the sides with a bench scraper.

Pipe remaining peanut butter frosting around the edge of the cake. Garnish with peanut butter cups, if desired. Serve cake immediately or chill before serving.