If you have two trays of ice cubes, you can have the ice cream mixture ready for churning in less than 20 minutes, by cooling the warm milk completely in an ice bath.
The smaller the quantity of the mixture you chill in the ice bath, the fewer ice cubes you need. So prefer to cool the warmed milk (from step 1) in the ice bath before adding the rest of the liquids. As soon as the milk is fridge-cold, you can remove it from the ice bath, add the cold cream and the rest of the cold milk and churn.
How to prepare an ice bath for fast chilling:
1. Put the milk in a bowl made of heatproof glass or stainless steel; these materials help the milk chill fast and do not break in sudden temperature changes. Avoid using a plastic bowl which will take forever to cool, or a regular glass bowl that may break upon contact with the ice bath.
2. Nest the bowl with the milk into a large empty bowl (it should be large enough to fit ice cubes on the sides) and fill the sides of the large empty bowl with ice cubes. How many ice cubes? Well, the more ice you put in, the faster it will chill.
3. Pour cold water into the sides of the large bowl, taking care that no water slips into the milk. Pour as much cold water as needed so that the level of the water bath in the large bowl is 2 cm / 1 inch above the milk.
For this quantity of milk, we started with approx. 300 g; 10 oz ice cubes and less than 1 litre fridge-cold water.
4. Refresh the ice bath with new ice cubes as soon as the older ones start to melt. If you have a thermometer, add enough ice cubes to keep the water well below 10° C / 50° F – take care that you measure the temperature of the water itself, not the ice temperature. The colder the ice bath, the faster the milk will chill. We used approximately 250 g; 9 oz additional ice cubes.
5. Stir often, leaving the spatula in the bowl during the cooling process. The milk is ready when it is fridge-cold to the touch (4-12° C / 39-54° F).
6. Remove the bowl with the milk from the ice bath, and wipe its bottom with a kitchen towel. Add the cold cream and the rest of the cold milk; the ice cream mixture is now ready for churning.