Dry-ice ice cream

Stir together the milk, cream, sugar and vanilla.

Handle the dry ice (surface about -109F / -78C) with gloves or a towel; pulverize it into a fine snow, the finer the better.

Stir the dry ice into the mixture one spoonful at a time; more than a spoonful locks the ice cream up hard. When the bubbling (sublimation) calms, add another spoonful. Work in a large, well-ventilated room.

After four or five spoonfuls the ice cream is soft-serve; fish out any big pieces of dry ice still visible.

Put the bowl in the freezer for about half an hour so any remaining dry ice sublimates away.

The ice cream is slightly carbonated and fizzy, with tiny ice crystals; the same mixture simply put in the freezer for a few hours forms large ice crystals.