1.Preheat the oven to 350°F and prepare two 9-inch round cake pans by greasing and lining them with parchment paper.
2.In a large bowl, whisk together the flour, granulated sugar, cocoa powder, baking soda, baking powder, instant coffee, and salt until well combined.
3.In another bowl, beat together the softened butter and buttermilk until smooth. Add the eggs one at a time, mixing well after each addition.
4.Gradually add the wet ingredients to the dry ingredients and mix until just combined.
5.Divide the batter evenly among the prepared cake pans and smooth the tops.
6.Bake in the preheated oven for 25 minutes or until a toothpick inserted into the center comes clean. Allow to cool in the pans for 10 minutes before transferring to wire racks to cool completely.
7.Mix the peanut butter and powdered sugar in a separate bowl until smooth.
8.Whip the heavy cream in another bowl until soft peaks form, then fold it into the peanut butter mixture until fully combined.
9.Once the cakes are completely cooled, spread the peanut butter frosting between the layers and on top of the cake.
10.Slice and serve to enjoy.