I made these for a family Christmas party and an end-of-the-year class party. I got a lot of great feedback from the people who tried a brownie. Beware: Be careful with the amount of Peppermint extract you use. It's very potent!
Preheat oven to 350 degrees F and grease a 9-inch square baking pan. For the brownies, place the btuter and chocolate in a microwave-safe bowl. Microwave on high for 1 minute, stir, and microwave for 1 minute more. Stir until smooth. In a separate bowl, whisk together the sugar and eggs. Stir in the chocolate and the vanilla extract. Finally, stir in the flour and salt until thoroughly combined. Pour into the prepared pan, then bake for 25 minutes or until a knife inserted in the middle comes out clean. Cool for at least 1 hour.
To make the mint frosting, cream the butter and confectioners' sugar. Add the milk 1 tbsp. at a time, beating until it is smooth and spreadable. Beat in the peppermint extract and tint to the desired shade with green food coloring. Frost the cooled brownies, cover, and chill for 1 hour.
To make the chocolate topping, pour the chips into a microwave-safe bowl, add the butter, and microwave on high for 1 1/2 minutes or until the chocolate melts. Stir until smooth. Pour the chocolate over the brownies and smooth it with a knife. Refrigerate for 45 minutes or until the coating hardens.
Bring the brownies to room temperature, then cut into 16 to 32 pieces.