In the smaller bag, combine cream, milk, sugar, and any flavoring you want. For vanilla, simply add vanilla extract. Remove as much air as possible from bag, before sealing tight.
Fill the larger bag halfway with ice. Add salt over the ice. Mix the bag to help distribute the salt.
Place the bag of ice cream mixture inside and seal the larger bag well. Shake the bag continuously for about 10-15 minutes, or until the mixture become firmer. Use a kitchen towel or oven mitts to protect your hands from the cold.
Remove the ice cream filled bag from the ice, wipe the bag clean from salt, and scoop out the ice cream to serve.