Instructions:

Make Meatballs: In a large bowl, gently combine all the meatball ingredients (meat, breadcrumbs, Parmesan, egg, parsley, garlic, salt, and pepper) using your hands. Do not over-mix. Roll the mixture into 1.5-inch balls.
Brown Meatballs: Heat olive oil in a large, heavy pot or skillet over medium-high heat. Brown the meatballs in batches on all sides, then remove them and set aside. They do not need to be cooked through.
Make Sauce: In the same pot, add the onion and cook until soft (2-3 minutes), then add the garlic and cook for 1 minute. Pour in the crushed tomatoes, and any extra seasoning (like a pinch of sugar or red pepper flakes). Bring the sauce to a simmer.
Simmer: Gently add the browned meatballs to the sauce. Reduce heat to low, cover, and simmer for 30-45 minutes, stirring very gently once or twice.
Cook Pasta: Cook the spaghetti according to package directions until al dente. Drain.
Serve: Serve the meatballs and sauce over the hot spaghetti, garnished with extra fresh parsley and Parmesan cheese.