Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking pan.
In a mixing bowl, combine melted butter and sugar. Add eggs and vanilla extract, and mix well.
Stir in cocoa powder, flour, salt, and baking powder until well combined.
Spread the batter evenly in the prepared pan. Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean. Let cool completely.
Once the brownies are cool, cut them into squares. Place a scoop of softened mint chocolate chip ice cream between two brownie squares to make a sandwich.
Wrap each sandwich in plastic wrap and freeze for at least 1 hour before serving.