Triple Chocolate-Nut Brownies
["nonstick cooking spray", "1 (21.5 or 23.7 oz.) pkg. fudge brownie mix", "1 (3 oz.) bar milk chocolate, chopped coarsely", "1/2 c. semi-sweet chocolate chips", "1 (1 oz.) sq. unsweetened chocolate, chopped coarsely", "1 1/2 c. mixed nuts from 12 oz. can, chopped coarsely", "1/4 tsp. ground cinnamon"]
["Heat oven to 350\u00b0.", "Line bottom and sides of a 9-inch square baking pan with foil, leaving a 2-inch overhang.", "Spray foil with nonstick cooking spray."]
["nonstick cooking spray", "brownie mix", "milk chocolate", "semi-sweet chocolate chips", "unsweetened chocolate", "mixed nuts", "ground cinnamon"]