For the sauce:
1 (14-ounce) or 1/2 (28-ounce) can whole peeled tomatoes in juice, preferably San Marzano
1 1/2 to 2 1/2 cups water
1 tablespoon tomato paste, preferably double concentrated
1 teaspoon beef base (available in some supermarkets and specialty food stores) or 1 beef bouillon cube
1 celery rib, roughly chopped
1/2 medium onion, roughly chopped
1/2 medium carrot, roughly chopped
3 tablespoons unsalted butter
2 ounces sweet Italian sausage, removed from casing
2 ounces pancetta or slab bacon, finely chopped
3/4 pound ground beef (not lean)
3/4 pound ground pork
1/2 pound ground veal
Fine sea salt
Freshly ground black pepper
1 cup dry red wine
1 bay leaf
3/4 cup whole milk
Freshly grated nutmeg

For serving:
Fresh tagliatelle, or other pasta, cooked until tender in salted water
Freshly grated Parmigiano-Reggiano cheese