In a large bowl whisk together the flour, cocoa, cornstarch, baking soda & salt.
In a separate large bowl beat the butter and sugars together until light & fluffy.
Beat in the egg, vanilla extract and food coloring.
With the mixer on low, beat in the flour mixture about ½ at a time.
Turn off the mixer and stir in the chocolate chips.
Cover the bowl with plastic wrap and refrigerate for 3 hours, or overnight.
When ready to bake, preheat the oven to 350F degrees. Line 2 cookie sheets with parchment paper or a silicone baking mat.
Using a cookie scoop, form dough into balls of about 1- 1.5 tablespoon in size and place 2 inches apart on the lined cookie sheets. Note: if the dough is too hard to form into balls, let the bowl sit on the counter for 10-20 minutes first.
Bake 1 cookie sheet at a time on the middle rack of the oven for 7-9 minutes, or until the tops look just set.
Remove from the oven and optionally, place a few white chocolate chips on the tops of each cookie. Cool on the cookie tray for 10 minutes, before transferring to a wire rack to continue cooling.