1. With an electric mixer, combine butter and sugar. Beat on meadium-high until light and fluffy, about 2-3 minutes.
2. Blend in the eggs one at a time. Scrape down the sides of the bowl to make sure all is well incorporated.
3. Mix in the cocoa power until well mixed.
4. Add the flour, salt and baking power and mix.
5. Add M&Ms with a spatula and make sure ingredients are well combined. Be aware that the dough is quite thick.
6. Break off pieces of dough and roll into balls of about an inch or so, then flatten a little bit into a disc. These cookies spread a little bit while baking, but not much.
7. Place on a parchment lined cookie sheet and bake at 350 degrees for 8-10 minutes.