Mix and bake brownies in a square pan according to the instructions on the back of the box. Allow them to completely cool about five minutes in the pan then lift out with foil handles. Allow to cool completely.
Remove brownies from the foil and cut into triangles. We cut out paper triangles measuring 2.5 inches wide at the base and 2.5 inches tall.
Snap the candy canes into 1.5" long pieces, or you can use pretzel sticks. If you do use pretzels, use two side by side since they are small. Press the broken end of the candy cane into the bottom of the brownie triangles.
Separate the frosting into three separate bowls. Tint two of the bowls of frosting with food coloring (blue and green). Fill sandwich sized zipper bags with each color of frosting. Seal and snip off the corner of each bag to make a piping hole.
Decorate the brownies with the colored frostings and various sprinkles and stars.
It's best to line your baking pan with aluminum foil then spray it with cooking spray. Allow excess foil to hang over the edges of the pan. This will give you handles to lift the brownies out with.
If your brownies are sticky, run the knife blade under hot tape water in between each cut. If you are still having trouble, refrigerate the brownies for a few hours to make them easier to cut.