In a large saucepan, melt the butter on medium heat.
When the butter is melted, add in the marshmallows mixing constantly until melted.
Remove from heat and mix in the vanilla and the black food coloring to your desired color. Fold in the Rice Krispie cereal until full combined.
Drop by spoonfulls onto a baking sheet lined with wax paper. It doesn’t need to be pretty, it’s coal!