Microwave butter in large microwaveable bowl on HIGH 30 sec. or until melted. Add marshmallows; toss to coat. Microwave 1-1/2 min. or until marshmallows are completely melted and mixture is well blended, stirring after 45 sec. Add cereal; mix well.
Press cereal mixture firmly onto bottoms and up sides of 24 lightly greased 2-1/2-inch muffin cups; cool. Store, loosely covered, at room temperature.
Fill with coconut and candies to resemble eggs in nests just before serving. Makes 2 dozen.