I first read about this simple pork roast braised in milk in Marcella Hazan's first cookbook The Classic Italian Cook Book: The Art of Italian Cooking and the Italian Art of Eating (1973), but you can find this well-known dish in many recipe books, including the venerable Artusi and Ada Boni's indispensable Talismano. If you have somehow missed trying this dish, it will be a revelation.
Season a pork roast (see below) with salt and pepper, then brown it in butter (or butter mixed with a bit of oil to retard burning) along with a clove or two of garlic and a sprig of rosemary in a Dutch oven or casserole in which the roast fits snugly. (Remove the garlic as soon as it begins to brown.) Pour enough milk to come halfway up the roast, cover and allow to simmer slowly until the pork is done and the milk has reduced and separated into dark brown curds and fat. If the pork is done before the milk has reduced—which is likely if you are using a pork loin or tenderloin—then remove it and keep it warm while the milk continues to simmer, then return the roast to the casserole to reheat when the sauce is ready.
If you are having a family-style meal, you're done. Just slice the roast, nap with the sauce and serve. It will not be particularly pretty but it will be very tasty. If you want a more elegant effect, then you can do one or both of two things: add some heavy cream to the milk, which will cause the sauce to amalgamate, and continue simmering until the sauce is dark and smooth (see photo). You can also blend the sauce (with or without the additional of cream) to a smooth and perfectly even consistency.
NOTES: The dish is simplicity itself, but there is one point you need to watch out for: the old recipes called for braising an arista (pork loin) for a couple of hours, enough time to allow the meat to become fork-tender and the milk to reduce completely. But these days pork (at least in the US) is bred for leanness, which means that cooking a loin for that long is likely to result in dry, overcooked meat. So try to find a pork loin with as much fat on it as you can, then carefully gauge the internal temperature after the first 30-45 minutes until you reach 65°C/150°F, at which point you can remove the roast from the casserole and let it rest while the sauce continues to simmer. The meat will continue to cook as it rests. (NB: The USDA recommends cooking to 70°C/160°F for health reasons, particularly pregnant women, children, the elderly and those with decreased immune function.)
In the alternative, you can use another cut of pork that will tolerate a longer cooking time without drying out, such as the shoulder. The taste will be lovely, but a shoulder roast tends to 'shred' when carved, so don't expect the neat little round slices you get from the loin.
Artusi's recipe (No. 551 in La scienza in cucina, if you're curious) calls for placing the pork roast raw into the milk and then browning it at the end, when the milk has reduced into fat and curds. He then tells you to remove the roast, skim off the excess fat and add some fresh milk, which will have the effect described above of turning all the curds into a smooth sauce. Boni's recipe calls for rubbing the roast the night before with salt and pepper and allowing it to marinate overnight, omitting the garlic and rosemary. She also suggests an elegant finishing touch of shaving white truffles on top of the roast. (Sounds wonderful, if you can afford it!)
Some other recipes call for using cream instead of milk—which is no doubt delicious, but might be a bit heavy for modern tastes. Hazan's recipe is even more austere than the one described here: like Boni, she omits the garlic and rosemary, seasoning the dish only with salt and pepper. Other recipes, on the other hand, call for the addition of some cloves (chiodi di garofano), sage and/or a bit of lemon zest; others call for a splash of cognac or other liqueur. If you prefer, after the initial browning, you can braise the roast in a hot oven (200°C, 400°F).
I find the ideal casserole for this dish is an oval, enameled cast iron Dutch oven, of the kind made by Le Creuset or Staub. The shape allows the roast to fit snugly, and the heavy cast iron ensures slow, even cooking.
