Open and place a sandwich bag into a stable cup and fold over the sides.

Add the half and half, sugar, and vanilla and stir until the sugar is dissolved.

Seal the bag and squeeze out the excess air at the same time, and place the bag into a second sandwich bag and seal.

Add half of the ice and salt into a gallon sized plastic bag, add the half and half mixture, and add the rest of the ice and salt, seal shut.

Wear oven mitts or wrap the bag of ice with a hand towel and shake for 10 minutes, until the half and half mixture thickens.

Carefully remove the small bag of ice cream out of the salt water and carefully remove the outer sandwich bag so that salt does not transfer onto the inner sandwich bag.

Eat and enjoy immediately.