1) For brownies: Heat oven to 350 degrees F. Grease an 8-inch square baking pan. Melt butter and chocolate in 2-quart saucepan over medium heat, stirring constantly, until smooth (4 to 6 minutes). Stir in sugar, flour and eggs until well mixed.
2) Bake for 25 to 30 minutes or until brownie begins to pull away from sides of pan. Cool completely.
3) Topping: Combine powdered sugar, cream cheese, butter, peppermint extract and green and yellow food colorings in small mixer bowl. Beat at medium speed until creamy. Spread over cooled bars.
4) Drizzle melted chocolate over topping. Cool completely; cut into bars. Cover and refrigerate if not serving immediately.