Preheat oven to 325° F.

Mix the first 3 ingredients in a bowl and set aside.

Using a hand mixer or standing mixer, combine the melted butter, sugar and vanilla.

Add the eggs one at a time until combined, then slowly mix in the dry ingredients until combined.

Pour the batter into a greased and parchment lined 9×13 baking dish and bake for 30 minutes.

Allow to cool completely, then cut out Christmas tree shapes using a cookie cutter. Note: Start on the edges and cut out the shapes close together so you can have as many trees as possible.

In a small bowl, mix powdered sugar and milk to create frosting. Put half of the icing in a separate small bowl and add green food coloring. Transfer the icings into two separate plastic ziplock bags. Remove excess air, seal the bags, and push the icing into one corner. Carefully snip a small hole in the corner for precise decorating.

Create a zigzag pattern by piping the green and white icings across the tree-shaped brownies. Add festive sprinkles immediately to complete the decoration. Serve and enjoy!