1. Preheat oven to 350°F and line a 9×13-inch pan with parchment paper.

2. Melt butter and whisk in granulated and brown sugar until glossy.

3. Stir in eggs one at a time, then add vanilla extract.

4. Sift flour, cocoa powder, baking powder, and salt, then fold into wet mixture.

5. Stir in chocolate chips and pour batter into the prepared pan.

6. Bake for 25 minutes or until edges are set and a toothpick shows moist crumbs.

7. Allow brownies to cool completely in the pan before lifting out with parchment.

8. Trim edges and cut the slab into long strips, then slice each strip into triangles.

9. Beat softened butter until creamy, then gradually add powdered sugar.

10. Add milk, vanilla extract, and green food coloring until smooth and pipeable.

11. Pipe frosting in zigzag lines on each triangle or spread with an offset spatula.

12. Insert a mini candy cane or pretzel stick at the base of each triangle as a trunk.

13. Decorate with sprinkles and press a candy star on each tip.

14. Let frosted brownies rest for 30 minutes until frosting sets before serving or gifting.