In a microwave-safe bowl, melt together the peanut butter and butter until melted. Stir until smooth.
Using a hand mixer (or a lot of arm power, beat in the powdered sugar until thoroughly combined. Mixture will be stiff.
Line a 9x9 baking pan with parchment paper. Press the peanut butter mixture into the pan until even and compact.
In a small bowl, melt the chocolate and 3 T peanut butter together in 30 second intervals in the microwave, stirring after each time until melted.
Pour over the top of the peanut butter and smooth out to the edges.
Place in refrigerator for 1 1/2 hours, or until firm. Cut into squares.