Melt the butter in a pot over low heat. Add the mini marshmallows and mix until fully melted. Remove from the heat and add the vanilla extract and green food colouring. Add the rice krispies and mix well.
Allow the mixture to cool until it is easily handled. Spray your hands with cooking spray and shape it into Christmas trees.
Roll the trees in colourful sprinkles, then set aside and cool completely.
Dust with confectioner’s sugar and enjoy!