Preheat and prepare the pans

• Preheat the oven to 175 °C.
• Grease and line the cake pans with parchment.

Mix the dry ingredients

• Whisk the flour, sugar, cocoa powder, baking powder, baking soda and salt together in a bowl.

Add the wet ingredients

• Add the eggs, buttermilk, vegetable oil and vanilla extract.
• Mix until just combined, then stir in the hot water until the batter is smooth.

Bake the cake layers

• Divide the batter evenly between the prepared pans.
• Bake until a toothpick inserted in the center comes out clean.
• Let the layers cool in the pans, then turn out onto a cooling rack.

Make the milk chocolate ganache

• Place the chopped milk chocolate in a bowl.
• Pour the warm heavy cream over the chocolate and let it sit, then stir until smooth and glossy.
• Let the ganache cool until thick and spreadable.

Make the peanut butter ganache

• Beat the peanut butter and butter together until smooth.
• Mix in the powdered sugar, then beat in part of the milk chocolate ganache until creamy and fluffy.

Assemble the cake

• Place the first cake layer on a plate or cake board.
• Spread a layer of milk chocolate ganache, then a layer of peanut butter ganache.
• Repeat with the remaining layers, then cover the top and sides with the remaining ganache.

Chill and serve

• Chill the cake until the ganache sets, then slice and serve.