In other words, I recommend not cutting into large pieces like you see below. I think I gave a sugar-high to the round of guinea pigs who tried the slices in the photo. :)
Chocolate Mint Brownies
1 1/2 cups (3 sticks) plus 6 tablespoons butter or margarine, divided
2 cups sugar
2 teaspoons vanilla
3/4 cup cocoa
1 cup flour
1/2 teaspoon baking powder
2 2/3 cup powdered sugar
1 tablespoon water
1 teaspoon mint extract
green food coloring
1 cup semi-sweet chocolate chips
Heat oven to 350 degrees. Grease 13 x 9 inch pan. Microwave 2 sticks of butter (1 cup) in large bowl until melted (about 2 minutes). Stir in sugar and vanilla. Add eggs and beat well. Stir in cocoa, flour, and baking powder. When well blended, pour into greased pan.
Bake 30 minutes or until toothpick inserted in center comes out clean. Cool completely on wire rack.
Once bottom layer has cooled, you can make the mint layer. Combine powdered sugar, 1 stick butter, water, and mint extract. Beat until smooth. Add about 4 drops of green food coloring and blend. Spread over top of brownies. Cover and refrigerate for an hour or two.
To make chocolate glaze, microwave 6 tablespoons butter and chocolate chips in small bowl for one minute. Stir until mixture is smooth. Allow to cool slightly. Then pour over mint layer. cover and return to refrigerate. Chill at least 1 hour before serving.