Preheat oven to 350 degrees. Cream softened butter and sugars. Scrape your bowl, then add vanilla and egg. Mix well and scrape bowl again. Begin slowly adding flour, baking powder and salt. Mix just until combined.
When the dough is completely mixed, add the chocolate chips and m&ms. Mix these in by hand. And I really do mean by hand. The best part of this is you get to lick the cookie dough off of your hands once the dough is mixed well.
Bake large cookies for 14 minutes and medium cookies for 12 minutes.