1. Measure KELLOGG'S® FROOT LOOPS® cereal and nuts into small mixing bowl. Sprinkle brown sugar over mixture. Add butter, tossing lightly until thoroughly combined.
2. Sprinkle half of cereal mixture evenly into buttered 8 x 8 x 2-inch pan; spread evenly with ice cream. Sprinkle with remaining cereal mixture, pressing lightly. Freeze until firm.
3. Cut into squares and serve with caramel or butterscotch sauce, if desired.