*Set the butter for the frosting out at room temperature to let it fully soften in advance!
Preheat your oven to 350 degrees F.
In a large mixing bowl, combine the sugar, oil, milk, eggs and vanilla extract. Mix well.
Brew one cup of coffee (it doesn't matter what kind, just whatever you drink at home as long as it's unflavored).
Add the hot coffee to the mixing bowl and mix again.
Sprinkle in the flour, natural cocoa powder, baking powder and baking soda. Fold the dry ingredients into the wet ingredients until a runny batter forms. Make sure there are no streaks of flour remaining (especially on the bottom of the bowl).
Grease a 9x13 inch pan and pour in the cake batter. Bake for 40-45 minutes.
For the frosting, combine the softened butter and peanut butter in a medium mixing bowl.
Whip the two together using an electric hand mixer until the mixture is very smooth and fluffy.
Add in the vanilla extract and milk, then mix to incorporate.
Sprinkle in the powdered sugar and switch to a rubber spatula for mixing to avoid clouds of powdered sugar flying everywhere!
Once the cake has cooled completely, spread the frosting all over the surface of the chocolate cake. If you like, you can use a spoon or offset spatula and make swooping motions with the frosting to give it a textured look.
Optionally chop up mini peanut butter cups and sprinkle them all over the top of the entire cake before serving!