Spray a 9x13 baking dish with nonstick cooking spray.
In a large pot, melt the butter over low heat. Stir in the vanilla extract followed by the marshmallows and stir continuously until melted and smooth.
Spread the Rice Krispie marshmallow mixture into the greased 9x13 dish. Gently press down to spread the mixture. I usually spray my hands with some nonstick cooking spray to make this process easier.
Decorate with sprinkles, if desired while the mixture is still not set.
Let the Rice Krispie treats cool for about an hour until set.
Flip the rectangle of Rice Krispie treats out of the dish. Cut out Rice Krispies with a tree cookie cutter. Spray the inside of the cookie cutter with nonstick cookie spray between cutting each one to prevent them from sticking.
Melt the candy melts in microwave according to package directions and add some green food coloring. Drizzle the melted candy over the christmas trees to decorate and decorate with more sprinkles and m&ms, if desired.
