Preheat oven to 375°. In a large bowl, cream butter and sugars until light and fluffy. Beat in egg, milk, food coloring and vanilla. In another bowl, whisk flour, cocoa, baking soda and salt; gradually beat into creamed mixture. Stir in baking chips.
Drop dough by tablespoonfuls 2 in. apart onto parchment paper-lined baking sheets. Bake 6-8 minutes or until set. Cool on pans 2 minutes. Remove to wire racks to cool.
Notes
Freeze option: Freeze cookies in freezer containers. To use, thaw before serving.