Preheat oven to 350. Coat 9x9 inch pan with cooking spray. Line the bottom and up two sides of pan with parchment. Prepare brownie mix according to package directions. Bake and cool completely. Beat 2 Tbsp. softened butter and 8 oz. cream cheese with a mixer until light and fluffy. Add milk and beat until blended. Slowly add powdered sugar and mix until thoroughly combined. Stir in peppermint extract. Spread peppermint frosting evenly over the brownies. Chill in freezer for 15-20 minutes. Place chocolate chips and remaining butter in bowl. Microwave in 30 second increments until melted. Stir until smooth. Spread evenly over cream cheese layer and top with crushed candy canes. Chill brownies for at least 30 minutes until chocolate is set.