Put the milk, vanilla and sugar into a quart-sized freezer bag. Squeeze out the majority of the air and seal well. Fill a large, gallon-sized freezer bag with ice. Add the salt. Put the smaller bag into the larger bag and seal. Now shake and mix until the ice cream thickens, about 10 minutes. Fun for parties, or kids. You should use gloves or a towel as the bag gets pretty cold.
You can also do this with a large coffee can. Put the quart sized bag inside of the can and surround it with the ice and salt. Great for kids to roll around and shake.
Makes 1 serving