This recipe is adapted from Anne Mendelson's "Milk: The Surprising Story of Milk Through the Ages" (Knopf, $29.95). You will need an instant-read thermometer, and a wide, shallow nonreactive skillet that will hold the milk without spilling when moved from one spot to another. Your milk need not be raw (nonpasteurized) but it must be unhomogenized.
2 quarts unhomogenized milk
2 cups nonultrapasteurized heavy cream, preferably unhomogenized
1. Combine milk and cream in a shallow nonreactive pan with a heavy bottom. Let it stand at least 12 hours, loosely covered, in a cool room. (You can use the refrigerator but the milk won't clot as firmly; increase the standing time to 16 to 24 hours or until the cream layer is well defined.)
2. Set a heat diffuser on a stove burner (or stack 2 grates on top of one another) and very carefully set the pan of milk on it over the lowest possible heat.
3. Watch the pan closely through the various heating stages. The slower the process the better. First you will see tiny beads of fat appearing just around the rim of the pan. Then small blistery stipplings will form just under the surface, which will begin to look filmy. Eventually the surface will acquire a yellow cast and begin to wrinkle, then coalesce into a more deeply and completely wrinkled crust. The milk will take on a faintly cheesey smell. The temperature, meanwhile, must reach something between 140 and 180 degrees and has to remain in that range long enough to encourage the maximum amount of clotting. Try to keep it within the right zone for 4 hours.
4. Very, very carefully remove pan from the heat, and let it cool to room temperature before sliding it into the refrigerator and leaving it there for at least 8 hours; the clot will not firm up until it is deeply chilled. With a slotted spoon, spatula or anything else that will work, gently lift the thick yellow crust into a small bowl, letting the residual milk drain back into the pan.
5. Part of the clotted cream with be firm, part will be slightly fluid. You can gently stir it together to even out the contrast, but I like it as is. It will keep in the refrigerator, tightly covered, for 5 to 7 days. Serve it on biscuits, scones, toast, bread or anything else that takes your fancy. It is a glorious partner to fresh fruit, and perhaps even better with compotes or stewed dried fruit. Makes about 1 cup clotted cream and 4 cups leftover milk.