5 star-shaped cookie cutters, in assorted sizes ranging from 2 to 5 inches
Line 15x10x1-inch pan with foil, with ends of foil extending over sides of pan. Lightly grease foil; set aside. Microwave butter in 4-qt. microwaveable bowl sprayed with cooking spray on HIGH 30 sec. or until butter is melted. Add marshmallows; stir with wooden spoon sprayed with cooking spray. Microwave 1-1/2 min.; stir. Microwave an additional 2 min., stirring after each min. Add cereal; mix well. Press firmly into prepared pan. Cool 15 min.
Lift cereal mixture from pan, using foil handles. Using cookie cutters, carefully cut two of each size star for a total of 10 stars; carefully peel off foil. Let stand until firm.
Spread half of the frosting onto tray to resemble snow. Stack prepared stars on tray, placing the largest stars on the bottom and smallest stars on top, rotating points of each star to resemble a tree and using the remaining frosting to attach stars to each other. Decorate as desired.