Line a 9×13-inch pan with parchment, leaving an overhang for easy lifting.
Stir melted butter, 1.25 cups peanut butter, vanilla, and salt in a large bowl until smooth.
Add powdered sugar and graham crumbs. Mix until evenly combined and dough-like.
Press the peanut butter mixture firmly and evenly into the lined pan.
Microwave chocolate chips with 0.33 cup peanut butter in 20–30 second bursts, stirring until silky.
Spread chocolate over the base. Tap the pan to smooth. Chill until set, then slice into 16 bars.