WHAT YOU NEED:
Ice
Kosher salt
Quart OR pint-sized Ziploc bags
Gallon-sized Ziploc bag
A few plastic grocery store bags
A towel to hold the very cold bag as you shake the ice cream
ALL YOU NEED TO DO IS:
1. Make & chill the ice cream base. Make sure your ice cream mix is well-chilled, preferably overnight.
2. Bag up ice cream mix, plus ice and salt. Put no more than 2 cups of the ice cream mix in a quart-sized baggie and seal securely. Fill a gallon-sized baggie halfway up with ice, then pour in about 1/2 cup kosher salt. Mix it around, then put the quart-sized baggie into the gallon-sized baggie. Make sure the smaller baggie is covered with ice.
3. Shake, shake, shake! Seal the larger bag securely and place it in a couple layers of plastic grocery store bags. Shake or rotate the bag for at least 5 minutes, preferably 10.
4. Open and check. Open carefully to avoid getting salt in the inner bag. The ice cream should be a soft mass by now. If not, close up again, add some ice and shake some more.
TIP: Turn the little bag inside out into a large bowl, carefully, to get all the ice cream out.