In A Large Microwavable Dish, Melt Butter. Stir In Brown Sugar And Maple Extract. Gradually Add Cereal, Nuts And Pretzels. Stir Well Between Additions. Coat All Pieces Well. Microwave On High For About 5 Minutes. Stir Every 1 1/2 Minutes. Spread On Waxed Paper To Cool. Store In Air Tight Container.