Preheat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

In a large mixing bowl, combine flour, sugar, cocoa powder, baking powder, baking soda, and salt.

Add buttermilk, vegetable oil, eggs, and vanilla extract to the dry ingredients. Mix until well combined.

Stir in boiling water until the batter is smooth.

Pour the batter evenly into the prepared cake pans.

Bake for 30-35 minutes or until a toothpick inserted in the center comes out clean.

Allow the cakes to cool in the pans for 10 minutes, then transfer to a cooling rack to cool completely.

In a mixing bowl, beat together peanut butter and softened butter until creamy.

Gradually add powdered sugar and heavy cream, mixing until smooth and fluffy.

Stir in vanilla extract.

Once the cakes are completely cool, place one layer on a serving plate.

Spread a generous amount of peanut butter frosting on top of the first layer.

Place the second layer on top and frost the top and sides of the cake with the remaining peanut butter frosting.

For optional chocolate ganache, heat heavy cream until simmering, then pour over chocolate chips in a bowl. Let sit for a few minutes, then stir until smooth. Drizzle over the frosted cake.