In large saucepan melt butter over low heat. Add marshmallows and stir until completely melted. Remove from heat.
2. Add KELLOGG'S RICE KRISPIES cereal. Stir until well coated. Add M&M's® chocolate candies. Gently stir until well mixed.
3. Using a spatula, press mixture evenly into a 13 x 9 x 2-inch pan lined with parchment paper. Bring parchment paper up on both ends to allow ease in removing from pan. Allow to cool.
4. Turn treats out of pan upside down. Remove parchment paper. Use Christmas Tree-shaped cookie cutter sprayed with cooking spray to cut out shapes.
In microwave-safe bowl, heat butter adn marshmallows on HIGH for 3 minutes, stirring after 2 minutes. Stir until smooth. Follow steps 2,3, and 4 above. Microwave cooking times may vary.