Preheat your oven to 350 degrees Fahrenheit. Grease your two cake pans with oil or butter.
Mix flour, sugar, and cocoa in a large bowl. Add the baking powder, soda, and a little salt.
Add the eggs, milk, and oil to the dry mix. Whisk everything until the batter looks very smooth.
Pour in the boiling water very slowly. Stir gently until the batter is thin and shiny.
Divide the batter between the two prepared pans. Bake them for thirty to thirty-five minutes total.
Let the cakes cool in the pans first. Then move them to a wire rack completely.
Beat the peanut butter and butter together. Add the powdered sugar slowly until it is fluffy.
Place one cake layer on a large plate. Spread a thick layer of frosting on top.
Add the second cake layer carefully. Cover the top and sides with the remaining frosting.