Heat oven to 350°F. In medium bowl, break up cookie dough. Stir or knead in 3/4 cup chopped candies. Shape teaspoons of dough into balls; place 1 inch apart on ungreased cookie sheets.
Bake 9 to 11 minutes or until set and edges are light golden brown. Cool 1 minute; remove from cookie sheets. Cool completely, about 15 minutes.
In small bowl, mix frosting ingredients until smooth, adding enough milk 1 teaspoon at a time until desired spreading consistency. Spread 1 teaspoon frosting on each cooled cookie. Cut each créme de menthe candy in half crosswise; cut each half diagonally into 2 triangles. Garnish each cookie with 2 candy triangles to form a tree.