Preheat your oven according to the instructions on your brownie mix box (or based on your homemade brownie recipe). Grease a 9 inch springform pan thoroughly with cooking spray or butter/oil.

Prepare the brownie batter. If you are using two boxes of mix, combine them as directed on the packaging. For homemade brownies, double the batch so you have enough batter for a thicker base. Pour the batter into the greased springform pan and spread evenly.

Bake the brownies for the time specified on the package or recipe, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.

Once baked, allow the brownies to cool completely in the pan. This cooling step is important so frosting does not melt when applied.

Remove the cooled brownies from the pan and place them on a cutting board. Cut the brownie slab into 8 equal triangular pieces.

In one small bowl mix some of the white frosting with red food coloring until you reach a bright festive red shade. In a second small bowl mix white frosting with green food coloring until you reach a vivid green. You may leave a portion of white frosting uncolored if you like.

Fill separate icing bags with red frosting, green frosting, and plain white frosting. Attach a large star frosting tip such as 1M to each bag to get nice textured swirls.

Decorate each triangle. For Christmas tree brownies, pipe green frosting in a zigzag tree pattern. Add edible gold stars at the tip as tree toppers and scatter white pearl sprinkles as snow or ornaments. For Santa hat brownies, use red frosting for the hat body and white frosting for the trim and pompom.

Once decorated, place brownies on a platter. Let frosting set for a few minutes before serving so decorations stay intact.

Serve with a glass of milk or a warm holiday beverage and enjoy the festive treat.