Preheat oven to 350°F (175°C) and grease two 9-inch round cake pans.
In a large bowl, whisk together flour, sugar, cocoa powder, baking soda, baking powder, and salt.
Add buttermilk, vegetable oil, eggs, and vanilla extract to the dry ingredients and mix on medium speed until combined.
Reduce mixer speed to low and gradually pour in the hot coffee; stir until the batter is smooth.
Divide batter evenly between prepared pans and bake for 30 to 35 minutes, or until a cake tester comes out clean.
Cool cakes in pans for 10 minutes before transferring to wire racks to cool completely.
For the frosting, beat softened butter and peanut butter until creamy; gradually add powdered sugar and 3 tablespoons of heavy cream, beating until light and fluffy.
Place one cake layer on a serving plate, spread a thick layer of frosting over the top, then place the second cake layer on top.
Frost the top and sides of the cake with the remaining peanut butter frosting.
Heat the remaining heavy cream until simmering, pour over chocolate chips, let sit for 5 minutes, then stir until smooth and drizzle over the cake edges.