Blend rosemary leaves and crackers in a food processor until they resemble fine crumbs. Add mustard, egg, salt and pepper. Tip mixture is a bowl with the mince, and work through to it is evenly combined. Using clean hands shape into approximately 24 meat balls. Drizzle with olive oil. Put into a large fry pan over a medium heat and cook until meat balls are nice and golden – keep them on the move so they do not stick. This should take 8-10 minutes.
Finely dice onion and garlic and brown these ingredients in a saucepan. Add tomatoes, vinegar and basil leaves and bring to the boil. Season with salt and pepper. Add the sauce into the pan with the meatballs and simmer gently. Cook spaghetti in boiled water according to packet instructions.
Drain and add half of the tomato sauce to the spaghetti (you’ll need to spoon it out from the meat ball pan). Place spaghetti on a plate with meat balls on top. Sprinkle with grated parmesan.