Soak the breadcrumbs in the heavy cream in a bowl.
Heat a large saute pan over medium heat and add the canola oil. Saute the onions and garlic until the onions are translucent. Add the rosemary, remove from the heat and then chill the mixture thoroughly.
Combine the breadcrumb mixture, onion mixture, pork, sausage, veal, Parmesan, parsley and egg in the bowl of large electric mixer and begin mixing on low speed. When relatively well incorporated, add some salt.
Heat a small saute pan to cook a sample of the mixture. Taste for seasoning and make any necessary adjustments. Form the meatballs into the desired shape and chill for 1 hour.
Preheat the oven to 425 degrees F.
Bake the meatballs on a baking sheet until browned, 20 to 25 minutes. Bring the Basic Tomato Sauce to a simmer. Transfer the meatballs to the sauce and simmer until tender and cooked through, about 30 minutes.
Bring a large pot of salted water to a boil. Boil the spaghetti until al dente according to the package directions.
Transfer the cooked spaghetti to the sauce with the meatballs and toss. Add some black pepper, garnish with Parmesan and parsley and serve.
Basic Tomato Sauce:
Heat a saucepan over medium heat. Add the olive oil, basil, garlic and red pepper flakes and cook until the garlic begins to soften, about 3 minutes. Add the tomatoes, bring the mixture to a simmer and cook for 1 minute. Use right away, or chill until ready to use.