This is from an awesome blog: picky-palate.com.
1 c. butter, chilled, cut into smallish slices
1/2 c. sugar
1/2 c. brown sugar
1 T. vanilla
2 1/4 c. flour
1 t. baking soda
1/2 t. salt
4 oz. box instant chocolate pudding mix
7 oz. peanut butter chips
1 1/2 c. mini marshmallows
Preheat oven to 350. Really cream the butter and sugars together. Add egg and vanilla. Add everything else except marshmallows. Drop onto cookie stone/sheet and smash marshmallows on top as if they were m&ms in a monster cookie. Bake 10-12 minutes.