In a large mixing bowl, cream the butter, brown sugar, and sugar. Then, beat in the vanilla, egg, and egg yolk. In a small bowl, heat the chocolate chips for 15-second increments until melted. Then, add to the batter. Next, use another small bowl to melt the Andes mints. Beat those into the batter. Finally, beat in the cocoa powder, baking soda, salt, and gluten free flour blend. Cover and refrigerate dough for at least an hour.