Season the pork roast with salt and pepper, then brown it in butter (or butter mixed with a bit of oil to retard burning) along with the garlic and 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 under the lowest possible heat 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.