If you watch any cooking shows at all, you will soon see some chef making ice cream using liquid nitrogen. There are a couple of reasons they do this. One is that — well, it's liquid nitrogen. If I had liquid nitrogen, I would use it whenever I could!
A more practical reason is that it makes great ice cream. The key to smooth ice cream is the smallest possible ice crystals and a great way to achieve that is very fast freezing. Liquid nitrogen is −196 °C (−321 °F).
A third reason is the ability to very quickly make ice cream to order, with any flavor they can imagine. It takes just a minute.
Well, I don't have liquid nitrogen. But dry ice, which is frozen carbon dioxide, is available at the grocery store, for around $1-2 a pound. At −78.5 °C (−109.3 °F), it's nowhere near as cold, but it's cold enough. And it's cool, both figuratively and literally.
The method is simple. Make any ice cream mix and refrigerate overnight. Get a pound of dry ice for each pound of mix. Break it into chunks with a hammer (this is fun).
Some recipes suggest using a blender for making the snow:
Fail. In our blender, at least, the blade could not reach the chunks, which jammed in the bottom. The food processor worked well.
Recipe: Dry Ice Ice Cream
1 vanilla bean (or 2 tsp vanilla extract — see note)
1 ¾ cups heavy cream
1 ¼ cups whole milk
½ cup sugar
⅓ cup light corn syrup
¼ teaspoon salt
6 large egg yolks
Caution: Be sure to read the precautions that accompany your dry ice. Basically, don't touch it and be careful in step 3 and 4 to avoid serving dry ice snow.
1. 4-24 Hours Ahead of Time: Cut vanilla bean in half lengthwise. Using tip of paring knife, scrape out vanilla seeds. Combine vanilla bean, seeds, cream, milk, 1/4 cup plus 2 tablespoons sugar, corn syrup, and salt in medium saucepan. Heat over medium-high heat, stirring occasionally, until mixture is steaming steadily and registers 175 degrees, 5 to 10 minutes. Remove saucepan from heat.
2. While cream mixture heats, whisk yolks and remaining 1/4 cup sugar in bowl until smooth, about 30 seconds. Slowly whisk 1 cup heated cream mixture into egg yolk mixture. Return mixture to saucepan and cook over medium-low heat, stirring constantly, until mixture thickens and registers 180 degrees, 7 to 14 minutes. Immediately pour custard into large bowl and let cool until no longer steaming, 10 to 20 minutes. Cover bowl with plastic wrap, place in refrigerator, at least 4 hours and up to 24 hours.
3. Place a strainer on the stand mixer's bowl and pour custard into bowl. Discard vanilla beans (or rinse, dry, and place in a jar with sugar to make vanilla sugar).
Using a hammer, break dry ice into pieces no larger than a golf ball. Drop into food processor and grind into "snow."
Place bowl on stand mixer and start mixer at medium speed. Add dry ice snow, a half cup at a time at first, then a tablespoon at a time as the ice cream begins to stiffen. As the mixture freezes, you will need to increase mixer speed. Continue until the mixture is ice cream consistency and the mixer becomes labored. If you add too much snow, it will collect at the bottom of the bowl, under the ice cream.
4. Scoop ice cream into bowls, being -very- careful to leave any dry ice snow deposits behind. Dry ice will burn the mouth. If you're worried about this, transfer ice cream to freezer overnight before consuming.
Ice cream can be stored in freezer for up to 5 days.
Note: Two teaspoons of vanilla extract can be substituted for the vanilla bean; stir the extract into the cold custard in step 3.