To prepare frosting, in a medium mixing bowl, cream butter and powdered sugar together.
Add 2 tablespoons of milk and vanilla. Beat well.
If it is too thick, add more milk. If it is too thin, add more powdered sugar.
Add green food coloring gel to frosting until desired color is reached.
Transfer frosting to a large pastry bag with a star-shaped tip.
Fill each cone with two mints and ¼ cup M&Ms.
Place a cookie over top to hold the candy in. Next, gently flip it over so the candy remains inside the cone.
Pipe frosting around the base of each sugar cone, securing each to a cookie.
Continuing adding frosting around each cone until they are covered entirely.
Add sprinkles to each tree to decorate them.
Top each tree with a star sprinkle.