In a large bowl, cream together butter and sugars. Add eggs and vanilla extract and beat until mixture looks fluffy, about a minute. Add red gel food coloring and milk, stirring to combine.
In a separate bowl, whisk (or sift) together the flour, cocoa salt, and baking soda.
Gradually stir dry ingredients into butter mixture until just combined.
Cover bowl or wrap dough in wax paper. Chill for at least 1 hour (up to 24 hours) in the refrigerator. Refrigerating will help the flavors meld and also create a firmer dough to roll into balls.
Preheat oven to 350 degrees.
Remove dough from refrigerator. Scoop dough using a 1.5 tablespoon scoop or shape by hand into 1.5 inch balls. Roll balls in granulated sugar.
Place cookie dough balls 2 inches apart onto a parchment lined baking sheet. Bake for 9-11 minutes, or until cookies begin to crack on top. Allow to cool for 5 minutes before removing to a wire rack to cool completely.
Your cookies will keep for 5-7 days in a sealed container. To help keep cookies fresh, you can place a slice of bread in the container with the cookies. Replace the bread slice as needed.
You can keep raw cookie dough in the refrigerator for 3 days. Cookie dough balls (and baked cookies) freeze well, up to 3 months in a sealed plastic container or freezer bag. Allow frozen balls to thaw for up to 10 minutes on the baking sheet before baking, or add 1-2 minutes to the baking time.
Red food coloring can be omitted if desired. However, cookies will turn out a medium brown color instead of red as shown.