Preheat your oven to 350°F (175°C).
Prepare a 9x9-inch baking pan by greasing it with butter or lining it with parchment paper.
In a large mixing bowl, combine cocoa powder, granulated sugar, brown sugar, and melted butter. Whisk until well combined.
In a separate bowl, mix gluten-free flour and salt.
Add eggs, vanilla extract, and peppermint extract to the cocoa mixture. Whisk until smooth.
Gently fold the dry ingredients into the wet mixture until no flour is visible.
Stir in the semi-sweet chocolate chips.
Pour the batter into the prepared baking pan and spread evenly. Bake for 25-30 minutes.
Let the brownies cool in the pan for 10-15 minutes before frosting and cutting.