1In a mixing bowl, mix together the butter and peanut butter until smooth.
Add 1/2 cup of the flour, the sugars, egg,baking soda, baking powder and vanilla extract.
Mix until all is combined Add the remaining flour and mix until incorporated.
Spray the baking pan with non stick cooking spray.
2Press dough into the bottom of pan and bake at 350 Degrees for 18 minutes.
Remove from oven and sprinkle on the marshmallows.
Return to the oven for 2 minutes.
3Melt chocolate chips in the microwave or double boiler.
Sprinkle M&M's on top of marshmallows so that they are evenly distributed.
Drizzle melted chocolate over the bars and refrigerate until set.