Preheat oven to 350ºF. Coat muffin tin with cooking spray and set aside.
Cream together butter and Truvia. Add egg and vanilla and mix.
Combine remaining dry ingredients and add to wet mixture. Mix and then add the milk and combine.
Scoop about 2 Tbsp. cookie dough and roll together in a ball. Press into muffin cup, spreading dough evenly on the bottom and 3/4 of the way up the sides. Repeat with remaining muffin cups & dough.
Bake in preheated oven for 8-10 minutes, or until golden brown.
In a plastic ziploc bag, combine coconut with a few drops of food coloring, seal and toss around until coconut is colored green.
In a medium-sized mixing bowl, blend together powdered sugar, milk, vanilla and butter until smooth.
When cookie cups are cooled, run a knife along the side of them and carefully extract from muffin tin. Fill each cup with a small spoonful of frosting. Sprinkle some green tinted coconut on top of frosting and wedge 2 or 3 M&M candies into coconut. Repeat with remaining sugar cookie cups. Serve and enjoy!