Ice Cream in a Bag

1 cup half-and-half or whole milk

2 tbsp sugar

1/2 tsp vanilla extract

3 cups ice

1/3 cup rock salt or kosher salt

1 small and 1 large zip-lock bag

Mix milk, sugar, and vanilla in the small bag. Seal tightly.

Put ice and salt in the large bag.

Place the small bag inside the large bag. Seal.

Shake, toss, and roll the bag for 5-10 minutes.

Open the small bag — ice cream!

Wrap the bag in a towel — it gets very cold.

Add mix-ins after it sets: sprinkles, chocolate chips.

The salt lowers the ice's freezing point — that's the science.