Preheat your oven to 350°F.
Add the all-purpose flour, Dutch process cocoa powder, salt, and baking powder to a medium mixing bowl or to the bowl of your stand mixer. Pour 1 tsp of instant coffee into the palm of your hand. Pinch the coffee between your fingers to break it down even further as you add it to the bowl. Whisk together all dry ingredients and set aside.
2 cups all-purpose flour, ⅔ cup Ghirardelli Unsweetened Dutch Process Cocoa Powder, 1 tsp salt, 1 tbsp baking powder, 1 tsp instant coffee
Add the softened salted butter, white granulated sugar, and light brown sugar to a large mixing bowl. Cream together on low/medium speed (approx. 2-3 minutes).
1 cup salted butter, ⅔ cup white granulated sugar, ¾ cup light brown sugar
Add the egg, egg yolks, vanilla extract, and milk. Mix on medium speed until well combined, scraping down the bowl using a spatula or spoon periodically.
2 eggs, 2 egg yolks, 1 tbsp vanilla extract, 2 tbsp milk
Add the dry ingredients to the wet ingredients and mix on the lowest speed until just combined. Scrape down your bowl with a spatula or spoon, paying particular attention to any dry ingredients stuck to the bottom. Add the chocolate chips and mini chocolate chips and mix on low until they are just incorporated into your dough. Do not overmix.
1 cup semi-sweet chocolate chips, 1 cup mini semi-sweet chocolate chips
Place a silicone baking mat or parchment paper on a half sheet pan. Pour the mini M&Ms into a shallow bowl.Scoop large balls of dough that measure approximately 3.5 tbsp. (This is a scant ¼ cup or about 2 generous scoops using a #40 cookie scoop). Roll the dough between your palms to form a ball before slightly flattening it between your hands to form a thick disc. Dip the top of the cookie in your bowl of mini M&Ms, pressing down firmly so the candies completely coat the top of the dough. Place the cookie on the sheet pan, M&M side up (obviously!). Press the dough down a bit more, until the cookie is about 3" wide. Repeat for the rest of the cookies, placing a maximum of 6 cookies on each half sheet pan. These cookies will spread quite a bit, so I do not recommend overcrowding your sheet pan! 1-1½ cups mini M&Ms
Bake the cookies for 12-14 minutes at 350°F, or until the edges of the cookies are set while the middle remains soft but not shiny. Do not overbake. Allow the cookies to sit on the sheet pan for 3-4 minutes before transferring them to a wire cooling rack.
Enjoy these extra chocolatey M&M cookies! Store any leftover cookies in an airtight bag or container. Since these cookies maintain their texture quite well for 1-2 days after baking, feel free to bake these ahead.