Preheat oven 375℉. Unwrap all the Andes Mints and chop up into small pieces. Set aside.
In a mixing bowl, sift together the flour, baking soda, baking powder and salt and set aside.
In another mixing bowl, cream together the butter and sugar until smooth. Beat in egg, milk, and mint extract.
Gradually blend in the dry ingredients and add the green food coloring. Mix until dough is evenly colored.
Fold in the chopped Andes mints (and chocolate chips if using).
Put dough in the refrigerator until the dough is cool (about 30-40 minutes)
Roll rounded teaspoonfuls of dough into balls.
Bake for 8-10 minutes. Let stand on cookie sheet for 2 minutes before moving them to wire racks to cool.
Notes
The longer you chill the dough, the more flavor will develop (it really helps that mint flavor to come alive!). The flour will also absorb more of the moisture so the thicker and chewier the final texture will be.Chilling your dough also helps these cookies not to spread as much while you bake them, so you get a thicker, chewier cookie.