Heat oven to 350°F. Grease bottom of 13x9-inch pan with shortening or cooking spray
Make brownie batter as directed on box. Spread in pan
Bake 22 to 25 minutes or until toothpick inserted 2 inches from side of pan comes out almost clean. Cool completely on cooling rack, about 1 hour
Using fork, break apart brownies into small pieces. Place brownies in large bowl. Stir in chocolate syrup until brownies are moistened. Set aside
Spray another 13x9-inch pan with cooking spray
In 6-quart Dutch oven, melt butter over medium-low heat. Add marshmallows stir until melted and blended, 2 minutes. Remove from heat. Stir in peanut butter until melted. Add cereal mix well. Using a spatula, press half of cereal mixture in bottom of pan
Top cereal layer with reserved brownie mixture press to make a lightly packed brownie layer. Spoon remaining cereal mixture over top, and spread to cover brownie layer, pressing firmly for an even top. Cool 15 minutes
In small microwavable bowl, microwave chocolate chips and 1/2 teaspoon oil uncovered on High 30 to 60 seconds. Stir until smooth. Drizzle over bars. Refrigerate about 40 minutes or until chocolate is set. Cut into 6 rows by 4 rows
