Mix Dry Ingredients: In a medium-sized bowl, mix flour, cocoa powder, baking soda, and salt and set aside.
Cream Butter and Sugar: In a large bowl add the butter, cubed. Use a hand-held mixer and beat the butter on high until creamy. Turn to medium speed and beat in the sugars. Then add the egg, milk, and vanilla extract and continue to beat until combined. Once combined, add food coloring and mix again.
Create Dough: Add the dry ingredients to the bowl and mix until a sticky dough is formed.
Chill: Cover the dough tightly with plastic wrap and chill for at least 30 minutes and up to 3 days in the fridge.
Preheat Oven: When ready to bake, preheat oven to 350 degrees. If you've chilled the dough longer than 24 hrs, let the dough sit at room temperature for 45 minutes before baking.
Roll Out Dough: Line baking sheets with parchment paper and scoop out a spoonful of dough. Roll into a ball and place on the baking sheet leaving 1-2 inches of space.
Roll in Sugar: Add confectioner's sugar to a small bowl and roll dough balls at least once in the sugar. Bake for 10-11 minutes. Cookies may not spread much, so while they are still warm, lightly press down on them to create crinkles in the top.
Bake: Add cookie trays to the oven and bake for 10-11 minutes.
Cool: Let cookies cool on the baking sheet for 5 minutes before transferring to wire rack.