In a medium bowl, cream the butter, peanut butter, granulated sugar, and brown sugar with an electric mixer until thoroughly combined. Add the eggs and vanilla. Mix well.

Whisk together the flour, cocoa powder, baking soda, salt, and instant pudding in a separate medium bowl. Slowly add the dry ingredients into the creamed mixture, mixing well. Stir in the M&M's. Cover the bowl with plastic wrap and chill for at least 30 minutes.

When ready to bake, preheat the oven to 350°F. Line baking sheets with parchment paper.

Roll the dough into 1-inch balls and place them on the prepared baking sheet.

Bake for 8 minutes. Allow the cookies to cool for 2 minutes on the baking sheet before removing them to a cooling rack to cool completely.