For the Brownies:

1. 1. Preheat your oven to 350°F (175°C) and grease a 9×9 inch baking pan.
2. 2. Melt the unsalted butter in a medium bowl over low heat or in the microwave. Stir in the cocoa powder until smooth.
3. 3. Add granulated sugar and mix well. Incorporate the eggs one at a time, beating after each addition.
4. 4. In another bowl, whisk together the flour and a pinch of salt. Gradually fold into the wet mixture until just combined.
5. 5. Stir in peppermint extract and chocolate chips.
6. 6. Pour batter into the prepared pan, spreading evenly. Bake for 25-30 minutes, or until a toothpick inserted comes out with moist crumbs. Let cool completely.

For the Frosting:

1. 1. In a medium bowl, cream together softened unsalted butter and powdered sugar until fluffy.
2. 2. Mix in peppermint extract and green food coloring until smooth.
3. 3. Spread frosting over cooled brownies and let set before cutting into squares.