Heat oven to 350°F. Spray 13x9-inch pan with CRISCO® Original No-Stick Cooking Spray. Place cereal in food processor bowl with metal blade (crush cereal in 2 batches if necessary). Cover; process until finely crushed (about 4 cups). Or place cereal in large resealable food-storage plastic bag; crush with rolling pin.
In large bowl, stir butter and corn syrup until well blended. Add crushed cereal; mix thoroughly. Press evenly in pan.
In large bowl, make brownie mix as directed on box, using oil, water and eggs and adding cinnamon. Stir in 2/3 cup of the chocolate chips. Pour brownie batter over cereal mixture. Sprinkle remaining 2/3 cup chocolate chips evenly over batter.
Bake 20 minutes. Sprinkle cinnamon-sugar evenly over brownies. Bake 14 to 18 minutes longer or until brownies are set when lightly touched in center. Cool 10 minutes; loosen edges but do not cut. Cool completely, about 2 hours. For brownies, cut into 6 rows by 4 rows.