Add the milk to the breadcrumbs and set aside for a couple of minutes.
Add the ground beef to a clean bowl along with the parsley, egg, Locatelli, salt, pepper, and the moistened breadcrumbs. Using clean hands, mix everything together until just combined, making sure not to work the meat too much (it can become tough).
Form the meatballs into golf ball-sized balls and set aside. You should get about 20 meatballs.
Add enough olive oil to a pot or a non-stick skillet with high sides to be about ½ inch deep. Turn heat to just above medium and let the oil heat up, but not TOO TOO hot. Once ready, add enough meatballs so that they have about ½ inch between them. Brown nicely on one side, then turn and brown on the other side. Remove with a slotted spoon to rest on a paper towel-lined plate. Fry the next batch if needed.
Once the meatballs are browned, remove most of the oil and fat, leaving behind about 1-2 tablespoons. Lower the heat to medium if you haven't already. Add the onion and a pinch of salt, and cook for about 5-7 minutes, or until the onion has softened.
Add the red wine and let it reduce to half. Then, add the can of tomato puree and stir. Fill the can about ¾ with water, swirling it around, then pour that into the sauce and stir. Keep the can handy in case you need to add some water later. Add the torn up basil and stir. Bring to a low boil, then gently add in the meatballs and reduce to a dancing simmer.
Let cook for about 1.5-2 hours, stirring occasionally. Watch the sauce and add more water if needed. After the 1.5-2 hours, taste as season with more salt if needed.
Serve with pasta, some more basil and plenty of Locatelli.