Heat oven to 350°F (325°F for dark or nonstick pan). Line 8- or 9-inch square pan with foil, allowing some to hang over edges of pan. Grease bottom and sides of foil with shortening or cooking spray. Make and bake brownies as directed on box for 8- or 9-inch square pan. Cool completely on cooling rack, about 1 1/2 hours. Freeze in pan 15 minutes. Using foil to lift, remove brownies from pan, and peel foil away. Cut into 4 rows by 4 rows.