Imagine a soft, rich, and moist peanut butter sheet cake, topped with a lusciously creamy peanut butter frosting. Every bite melts in your mouth, bringing a perfect balance of sweetness and nuttiness.

In another large bowl (or the bowl of a freestanding mixer fitted with a whisk), beat the butter and peanut butter ... to get a dollop of icing onto the side of the cake, then spread it gently ...