Homemade Ice Cream in a Bag

I saw this recipe for Homemade Ice Cream in a Bag on Family Fun a while ago and I've been meaning to do it with the kids. Maybe this weekend I can drag myself to the store and get the ingredients! (We all know that's not going to happen, but let me dream a bit.)

RECIPE INGREDIENTS:
2 tablespoons sugar
1 cup half and half
1/2 teaspoon vanilla extract
1/2 cup salt (The bigger the granules, the better. Kosher or rock salt works best, but table salt is fine.)
Ice cubes (enough to fill each gallon-size bag about half full)
1 pint-size ziplock bag
1 gallon-size ziplock bag

1. Combine the sugar, half and half, and vanilla extract in the pint-size bag and seal it tightly.

2. Place the salt and ice in the gallon-size bag, then place the sealed smaller bag inside as well. Seal the larger bag. Now shake the bags until the mixture hardens (about 5 minutes). Feel the small bag to determine when it's done.

3. Take the smaller bag out of the larger one, add mix-ins, and eat the ice cream right out of the bag. Easy cleanup too! Serves 1.

Note: One of the commenters on Family Fun said she adjusted the recipe for her pre-k class: My class (18) each had their own bag and I used 1/2 C. whole milk, 1 tbsp. sugar, 1/4 tsp. vanilla each bag.

If you have tried this, let me know what you think!