1. Preheat the oven to 350 F.
2. In the bowl of an electric mixer, combine the butter and sugar. Beat together on medium-high speed until light and fluffy, 2-3 minutes. Blend in the eggs one at a time, scraping down the bowl as needed. Mix in the cocoa powder until well blended.
3. Add the flour, salt and baking powder to the bowl and mix on low speed just until incorporated. Fold in the M&M candies with a spatula.
4. The dough is very thick! Transfer the dough to a work surface and knead briefly by hand to be sure the ingredients are well combined. I kneaded mine in the bowl, and that worked out just fine.
5. Using a standard size cookie scoop, scoop cookie dough onto cookie sheets. To make 36 cookies, 12 cookies should fit onto each sheet.
6. Bake for approx 10 minutes. Let cool for 5-10 minutes on cookie sheets, then transfer to a wire rack to cool completely. Store in an airtight container. Enjoy!