Line an 8x8 or 9x9 square baking dish with foil and set aside.

In a medium bowl, mix together the melted butter, vanilla wafer cookie crumbs, and powdered sugar until combined.

Stir in the peanut butter.

Spread mixture into prepared pan.

In a microwave safe bowl melt the baking bits until melted.

Spread melted baking bits on top of peanut butter mixture.

Sprinkle marshmallow over the chocolate layer.

Refrigerate for 45 minutes or until set before cutting into squares.