Preparation Steps

• Preheat oven to 350°F. Line a half-sheet pan with parchment paper and set aside. If you plan to bake multiple batches, have an extra pan ready.
• In a large mixing bowl whisk the cooled melted butter with both sugars and the salt until mostly combined. You do not want to cream air into the mixture; a few streaks are fine.
• Beat in the vanilla and the eggs one at a time, mixing just until the batter is smooth and glossy. Scrape down the bowl so everything is evenly incorporated.
• In a separate bowl sift together the flour, black cocoa, Dutch-process cocoa, baking soda, baking powder, and instant espresso powder. Stir to distribute the leaveners and cocoa evenly.
• Fold the dry ingredients into the wet in two additions with a spatula, gently combining until no large streaks of flour remain. Avoid overworking to keep the cookies chewy.
• Stir in the dark chocolate chips with a spatula, then fold in about half of the M&Ms so the mix is distributed but not crushed.
• Cover the bowl and chill the dough in the refrigerator for at least 30 minutes, preferably 2 hours or overnight — chilled dough spreads less and develops more flavor.
• Using a 3-tablespoon scoop (or two rounded tablespoons), portion dough onto the prepared pan leaving 2–3 inches between mounds. Press a few extra M&Ms into the tops of each mound now if you like a colorful surface.
• Bake in the center of the preheated oven for 11–14 minutes: 11–12 minutes yields a softer center, 13–14 minutes gives a chewier edge. If baking from frozen add 1–2 minutes. Rotate the pan halfway through baking for even color.
• As soon as the cookies come out of the oven, gently press 1–2 candy monster eyes into each warm cookie so they adhere. Let cookies cool on the pan for 6–8 minutes, then transfer to a wire rack to finish cooling.
• Store baked cookies in an airtight container layered with parchment for up to 3 days at room temperature, or freeze unbaked scooped dough on a tray and transfer to a freezer bag for up to 3 months.