In the small resealable plastic bag, put together the milk, vanilla, and sugar. Push out excess air and seal tightly.
Combine ice and salt in the gallon-sized plastic bag.
Place the small bag inside the bigger bag, then seal.
Shake the bag vigorously for about 7 minutes until mixture inside the smaller bag has hardened.
Without opening the bags, allow them to rest on a plate or towel for another 1-2 minutes.
Unseal the bags and scoop out the ice cream from the smaller bag.
Serve with your favourite toppings!