I'm pretty sure I've done this a couple of years ago, but it bears repeating.
Looking for a way to entertain the kids for a while? A fun picnic dessert, perhaps? Ice cream in a bag will leave people wondering if you've gone off the deep end, and the kids will like it. You can even sneak a little bit of science education in there, while they aren't looking.
This idea came to me from Calvert School, although I've revised the recipe a bit from what they offered.
The first time I did this with my little boys, they were depressed because many of the big kids had just left for college. So when they got up that day, they found a big cardboard box labelled "Box Of Fun" on the kitchen table. Slicing it open, they found the necessary items and instructions for "Ice Cream in a Bag"! Entertaining, right? Well, OK, maybe not yet.
Here's what you need:
1 cup whole milk
1/4 cup heavy cream
1 tsp vanilla extract
1/4 cup sugar
1 quart sized Ziploc bag (with double zipper)
1 gallon sized ziploc bag
4 cups ice (minimum)
1/4 cup salt
cups and spoons
In the smaller Ziploc bag, carefully pour in the sugar, vanilla, cream and milk. Squeeze out as much of the air as possible, and zip it closed. Put half the ice in the bigger bag, along with the salt; put in the milk filled bag and add the rest of the ice. Shake it around. A lot. It will take 15 to 20 minutes. You may want to add more ice and salt as it melts. Wrap the bag in a towel for easy grasping, and/or pass it from person to person for shaking. When the ice cream has solidified (it will still be quite soft), scoop it into the cups. Serves 2 to 3.
The science behind this: Salt reduces the freezing point of water, so even though the ice melts, it's colder than 32F, and it will freeze the milk mixture. (See? Simple and painless, the kids will remember this. It's also why salt melts ice on driveways and streets, and here in the northeast we are cursed with body rot. I mean on our cars; on our persons, salt is not to blame.)
Variations to this recipe include adding 1/4 cup of diced frozen fruit, such as blueberries, strawberries or peaches, or 1/4 cup of chocolate chips, which can also be frozen, or replacing the vanilla with 1/2 tsp of peppermint extract, a couple of drops of green food coloring, and the chocolate chips. Add sprinkles and/or chocolate or strawberry sauce to the top for even more fun.
Have fun, and remember, let the kids have some!