I got this recipe from Deals to Meals who got if from Jamie Cooks it Up!
Yield: 48 cookies
Time: 1 hour
1 C butter, softened
1 1/2 C sugar
1 1/2 t vanilla
3 C flour
2 t baking powder
1 t baking soda
2 t cream of tartar
dash of salt
1 medium bag (12 oz) M and M's
1. In a stand mixer, or with hand held beaters cream the butter and sugar for about 3 minutes, or until fluffy.
2. Add the eggs and vanilla and mix for 2 more minutes.
3. In a separate small mixing bowl combine all dry ingredients. Add to the butter mixture and mix until well combined.
4. Pour in your M and M's and mix just until combined. Don't mix too long here guys and gals...you will crush your M and M's into smithereens.
5. Form into round balls (about 2 inches in size) and lay onto a cookies sheet. I like to smash the dough down just a little bit with the palm of my hand.
6. Bake at 350 for 8 minutes (about 6 minutes at 325 in a convection oven) or until you see the cookies start to crack. Take them out of the oven and let them finish cooking on the hot sheet for about 5 minutes.
7. Remove from the cookie sheet onto a wire rack to finish cooling.