Step 1: In the small (quart-sized) sealable plastic bag, combine the heavy cream, granulated sugar, and vanilla extract. Squeeze out as much air as possible before sealing it tightly. This prevents ice crystals and promotes faster freezing.
Step 2: Fill the larger (gallon-sized) sealable plastic bag about halfway with ice.
Step 3: Pour about 1/2 cup of rock salt (or coarse kosher salt) over the ice in the gallon bag. The salt is essential for lowering the freezing point of the ice, allowing the ice cream mixture to get cold enough to freeze.
Step 4: Place the sealed small bag containing the cream mixture into the larger bag with the ice and salt. Make sure it’s nestled securely amidst the ice.
Step 5: Seal the gallon bag tightly, again trying to remove excess air. If you’re worried about leaks, you can place this entire gallon bag inside another gallon bag.
Step 6: Now for the fun part! Vigorously shake, squish, and massage the bag for 7-10 minutes. This might feel like a workout, but it’s crucial for the ice cream to form. Wear gloves or wrap the bag in a kitchen towel to protect your hands from the cold.
Step 7: After 7-10 minutes, carefully open the large bag and inspect the small bag. The mixture inside should have thickened and solidified into creamy ice cream! If it’s still too soft, reseal and continue shaking for a few more minutes.
Step 8: Once your ice cream is ready, remove the small bag. Wipe off any salt water from the exterior of the small bag to prevent your ice cream from tasting salty. Spoon your freshly made ice cream into bowls and enjoy immediately!