Line a 9x9” pan with foil and spray with nonstick cooking spray.

Stir melted butter, cracker crumbs, 3/4 cup peanut butter, and powdered sugar in a large bowl until smooth. Mixture will be thick. Stir in mini marshmallows. Press into prepared pan.

Melt chocolate chips with remaining 2 tablespoons peanut butter. Heat on high for 30 second increments, stirring between each, until melted and smooth. Spread over the top of the bars.

Chill the bars to let them set, then slice into squares.

Store in an airtight container in the refrigerator for up to 4 days.