Heat oil in a mid-size heavy pot over medium heat. Sauté onion, stirring frequently, until soft, 8–10 minutes. Add garlic and continue, stirring occasionally for another 5 minutes; stir in chopped basil. Add tomatoes, crushing with your hands as you go; season with salt and pepper and simmer. Reduce heat; simmer gently, stirring occasionally, until sauce is thick, at least an hour. Sauce can be made a few days ahead if kept in the refrigerator.

Tenderize flank steak evenly. Add garlic, basil and season to taste. Sprinkle small handful of parmesan cheese. Roll up flank steak tightly and secure with string. Brown flank steak in pot with olive oil and a dash of vermouth, rotating until all brown. Take out. Make sauce and then add meatballs and add flank steak and meatballs into sauce and simmer on low for two to three hours.  

For the polpette meatballs, combine ingredients into a large bowl, saving a little bit of the breadcrumbs to roll the meatballs in before frying. Shape into balls and bake or fry. Add to sauce.