In a medium sized pot, melt butter over low heat. Add peanut butter, butterscotch chips & vanilla. Stir until everything is melted and combined. Fold in marshmallows.

Spread in an square baking pan (8 x 8 or 9 x 9). Refrigerate until firm. Remove from pan and slice into squares. Store squares in refrigerator or freezer.

Tips: Freeze marshmallows before folding in. This will ensure that your marshmallows will not melt in the peanut butter mixture.