Heat oven to 350 degrees. Line a 9x9 baking dish with foil or parchment paper. If using foil, grease or spray bottom of foil. Make sure parchment paper or foil extends about 2 inches over sides of pan.
Make brownies per instructions on box. Cool completely, about 1 1/2 hours. Remove from pan by lifting foil or parchment paper. Peel foil or parchment paper away.
Cut brownies into 3 even rows. Cut each row into triangles. (Snack on corner ends).
Place frosting into a bowl and add green food coloring until desired color is achieved.
Place frosting into a piping bag or storage bag and cut the bottom piece off. Squeeze bag to pipe frosting on brownies. Sprinkle with decorations of m&ms and sprinkles.
Break of curved end of candy cane and insert straight into bottoms of triangles to make tree trunks.
Enjoy.
