1Whisk flour, cocoa powder, baking soda, baking powder, and salt together in a bowl.
2Beat butter with an electric mixer until fluffy, about 2 minutes; beat in brown sugar and white sugar until smooth, about 1 minute. Beat egg, milk, and vanilla extract into butter mixture; beat in food coloring until uniformly colored.
3Stir flour mixture into butter mixture gradually with electric mixer on low speed until combined; stir in 1 cup chocolate chips. Cover bowl with plastic wrap; place in the refrigerator for 1 hour or up to overnight.
4Preheat oven to 350 degrees F (175 degrees C). Line baking sheets with parchment paper.
5Roll dough into 2-inch balls; place on prepared baking sheets and flatten slightly.
6Bake in the preheated oven until edges are lightly browned, about 10 minutes. Sprinkle cookies with a few additional chocolate chips; allow to cool completely.
Footnotes
Cook's Note:
Chilling the dough is highly recommended; it really does make a difference in the texture of this cookie. You can substitute white chocolate for the dark chocolate chips, for a nice contrast in color. If chilled overnight, remove dough from refrigerator about 30 minutes before working with it.