Heat a generous amount of olive oil in a large casserole (Dutch oven). Brown the meat in batches, so the casserole is not crowded.
The meat should be nicely browned on the outside, but remain raw on the inside. Reserve the meat and allow to cool. Once it has cooled down to room temperature, put it in the refrigerator (covered with plastic wrap).
The drippings that will be left in the casserole contain a lot of flavor, so make sure to use them for the sauce.
Add minced celery, carrot, onion, prosciutto, and pancetta to the drippings. Add more olive oil if needed.
Brown this mixture over medium-high heat, stirring regularly, until it starts to sizzle (indicating that most of the moisture is gone).
Add the wine. Bring to a boil and cook until most of the wine has evaporated, stirring regularly.
Add the tomatoes. Stir and bring to a boil, then reduce the heat to a nice simmer.
Add any juices that will have leaked from the reserved meat. Add freshly grated nutmeg. Allow the sauce to bubble over low to medium heat until it is no longer 'watery', stirring regularly. This could easily take an hour.
Add the milk. Stir and bring to a boil again, then allow to reduce over low heat, stirring regularly until the sauce has reduced to the right thickness. There will be no more reduction after this. Again this could easily take an hour.
Season to taste with salt and freshly ground black pepper.
Allow the sauce to cool. You can speed up this process by immersing the casserole in cold water.
While the sauce is cooling, it is time to grind the meat. Take it out of the refrigerator and cut it into chunks that will fit into the feeding tube of the meat grinder. As you can see, the meat is still raw on the inside. Grind the meat until you have ground all of it.
Once the sauce has cooled to room temperature, add the ground meat. Add two teaspoons of salt. Stir to mix it well.
Vacuum seal in individual portions. 300 grams (10.5 oz) of ragù is 2 servings. The easiest is to use a chamber vacuum sealer. If you don't have one, you could probably vacuum seal the ragù using a FoodSaver-type vacuum sealer once the ragù has cooled down in the refrigerator. If not, you could also freeze it first (in open bags) and then vacuum seal once frozen. Or use Ziploc bags and the water displacement method.
Cook the ragù sous vide for 24 hours at 165°F (74°C). It is probably most efficient to cook the whole batch at once, and freeze what you don't need at once to reheat later. If you freeze the ragù in a flat shape, you can defrost and reheat it at 165°F (74°C) in about an hour.
To dress pasta with the ragù, preheat a pan over low heat and pour the contents of a bag into it. Taste and adjust the seasoning with salt and freshly ground black pepper.
Add the cooked and drained pasta together with freshly grated parmigiano reggiano (about 25 grams or 1 oz for 2 servings). Stir to mix.
Serve at once on preheated plates, sprinkled with some more parmigiano.