Stir crushed candy into ice cream. Cover and freeze until ready to use.
Combine cereals, brown sugar, and remaining ingredients in a large bowl, stirring until well blended. Press half of cereal mixture in bottom of a 13 x 9-inch baking pan.
Let ice cream stand at room temperature 20 minutes or until softened. Spread softened ice cream mixture over cereal mixture; top evenly with remaining cereal mixture. Cover and freeze 8 hours or overnight.