Preheat your oven to 350°F (175°C) and grease two 9-inch round cake pans.
In a large bowl, combine flour, sugar, cocoa powder, baking powder, baking soda, and salt.
Add eggs, milk, oil, and vanilla to the dry ingredients and mix until smooth.
Gradually stir in boiling water until well combined.
Divide the batter evenly between the prepared pans.
Bake for 30-35 minutes or until a toothpick comes out clean.
Let the cakes cool in the pans for 10 minutes before transferring to wire racks.
Meanwhile, whip cream until soft peaks form.
In a separate bowl, beat peanut butter until creamy, then fold in whipped cream.
Once cakes are cool, spread peanut butter frosting between layers and on top.