Preheat your oven to 350 degrees fahrenheit, and spray a 9x13 inch pan with non-stick spray, set aside.

Prepare the brownie mix, according to the box directions.

Pour the batter into your prepared pan and bake according to the time recommendation on the box, about 25-30 minutes.

Allow the brownies to cool completely.

Once the brownies have cooled, cut out your triangle brownie pieces by cutting the entire pan of brownies in half length-wise. Then, divide the halves into triangles. You may have some extra brownie left on the ends that you can discard, or set aside.

Remove the triangle brownies from the pan to decorate!

Start by preparing the frosting.

Use a hand mixer to beat the sticks of butter until smooth.

Add powdered sugar and beat to combine the sugar and butter until fluffy.

Add the vanilla, and 1-2 tablespoon of milk. Mix to combine.

If needed, add the last tbsp. Of milk to reach your desired consistency.

Finally, add a generous amount of the green gel food coloring and mix to incorporate, adding more if needed, until you reach your desired shade. If your frosting becomes too thin, add 2 tablespoon of powdered sugar at a time, and mix, until you reach your desired consistency.

To decorate, add a squiggle of the green frosting to your tree brownies, and top with Christmas sprinkles.

Enjoy, and refrigerate any leftovers.