Fill a deep, wide-mouthed bowl with the cream and the milk.
Leave the mixture in the refrigerator for several hours (preferably overnight).
Heat the oven to 180 degrees F.
Boil several cups of water and pour it into a pan large enough to accomodate the bowl of milk.
Place the pan into the pre-heated oven.
Set the bowl of milk into the pan of water in the oven and leave until the top of the milk is crusted with a nubbly yellowish-cream surface.
(This will take at least 1 1/2 hours, but it is prudent to allow longer since this process varies depending on the fat content of the milk and cream).
Once the surface is nicely crusted, remove the bowl from the pan and cool it rapidly in a bowl of ice water.
Place the cooled bowl in the refrigerator until very cold.
Remove the crust from the cream with a skimmer or a large slotted spoon and put it into another bowl with a bit of the creamy liquid underneath; as the clotted cream firms up you will need to stir in the liquid to achieve a nice consistency.
Put the milk bowl back into the pan of water in the oven for a second crust to form, and add that in its turn to the first one.
Note: The left over milk is great to make rice pudding, or can be used in baking.