Coarsely grate the courgette into a large teatowel and then ring the teatowel to squeeze out all the excess water. Tip into a bowl and mix together with half the finely chopped onion, chopped rosemary, egg yolk and pork mince and season. Shape into 24 small balls and chill for 10 minutes.
Heat half the olive oil in a large frying pan, add the meatballs and fry in batches for 5-8 minutes or until golden all over.
In a separate pan, heat the rest of the olive oil, add the remaining onions and fry over a medium heat for 2-3 minutes or until softened. Add the Goodness tomato pasta sauce and a splash of water to loosen and warm through. Tip in the cooked meatballs and heat through.
Cook the spaghetti according to the packet instructions and drain.
Divide the spaghetti between 6 bowls, top with the meatballs and tomato sauce and scatter with grated parmesan to serve.
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Freezing and defrosting instructions
The meatballs can be made up to the end of paragraph three, cooled and then frozen for up to a month in the tomato sauce. Defrost thoroughly and then heat through until bubbling hot before serving.