Line a 13X9 pan with foil. Grease or spray with Pam. Combine marshmallows, butter, and chocolate in a microwavable bowl. Mike for 4-6 min. checking and stirring every 2 min. until melted. Stir in Rice Chrispies and coconut. Spread in pan quickly using a buttered spatula. Chill. Cut into small bars, finger size. I double this recipie and use a cookie sheet. They are a hit whenever I make them.