In a large saucepan, melt butter.

Add in marshmallows and stir continuously until fully melted and mixed with the butter.

Remove from heat and fold in rice krispies.

Dish into a 9 x 13 in baking pan.

Wet hands and evenly press mix into the pan.

Pour M&M's® out on top of the pressed treats and use a paper towel to gently press them into the treats.

Let set for 15-20 minutes before cutting.