In a large sauce pan or soup pot, melt the butter over low heat. While that is melting, butter a 9 x 13″ cake pan with cold butter (ie grease it).
Once the butter is melted, add in the marshmallows and marshmallow creme. Stir until mostly melted (I like leaving a few intact marshmallows for texture).
Then stir in the 6 cups of Rice Krispies cereal until mostly combined.
Spread into the buttered 9 x 13″ pan using a buttered spatula (so it doesn’t stick). Then sprinkle on a good layer of sanding sugar.
Once the bars are cooled, you can cut and serve them as squares or you can make them more festive by cutting them into triangles and then cutting out notches to make them look like trees.
To store: keep covered at room temperature.
Recipe Notes
You can easily double this recipe if you are wanting more than 15-20 treats!