Preheat oven to 350°F (175°C) and prepare an 8x8 inch baking pan.

In a large mixing bowl, cream softened unsalted butter with granulated sugar until smooth. Add eggs one by one and mix, then add peppermint extract.

In another bowl, whisk cocoa powder and all-purpose flour, then fold into the wet mixture carefully.

Fold in chocolate chips until evenly distributed throughout the batter.

Pour the batter into the prepared pan, spreading evenly, and bake for 25-30 minutes. Check for doneness with a toothpick.

Let the brownies cool in the pan, dust with powdered sugar, cut into squares, and optionally drizzle with melted dark chocolate before serving.