In a large bowl, mix beef, pork, and veal with the two types of breadcrumbs, parsley, parmesan, salt, pepper, nutmeg, egg, and ¾ cup of water with a fork.
Form the mixture into 14-16 2-inch meatballs.
Fill a 12-inch skillet with equal amounts of vegetable and olive oil, so you have ¼-inch of oil in the skillet.
Heat the oil, then reduce the temperature to medium-low, and sear the meatballs in batches, turning them carefully, so they brown all over. Take care not to overcrowd the pan. Each batch should not take longer than 10 minutes to sear. Once the meatballs are done, place them on paper towels to drain.
Throw away the oil, but do not clean the skillet.
For the sauce, add the olive oil to the same pan, then once heated, sauté the onions over medium heat for about 5-10 minutes until softened. Next, add the garlic and saute for a minute more.
Pour in the wine, up the heat to high and cook, scraping all the stuck pieces on the bottom of the pan. Cook for about 3 minutes, until the liquid evaporates, then add the tomatoes, parsley, salt, and pepper.
Add the meatballs to the sauce and cover the skillet with a lid. Reduce the heat until it simmers. Cook for 25-30 minutes until cooked through.
Arrange the sauce and the meatballs on cooked spaghetti, sprinkle with grated parmesan cheese and serve.
