Inside a quart sized freezer bag: 1c milk (whole or even half and half) 1T sugar 1/2 t vanilla seal with duct tape (the silver one)
Put this bag inside a gallon sized freezer bag then fill about 3/4 full with ice and put about 6T of rock salt.
Seal the bag.
Shake and mix for about 5-10 minutes...your hands will get cold.
Then take the inside bag out of the other bag and rinse it off; then open it and serve.
Put sprinkles or whatever on it.