Melt in the middle meatballs

Method

1. Put the mince in a bowl with the breadcrumbs, oregano and egg
2. Season and mix everything with your hands, then shape into 12 balls
3. Push your thumb into the middle of a meatball, then stuff the hole with a piece of mozzarella and reshape the meat around it
4. Repeat until all of the meatballs are stuffed
5. Chill in the fridge for 15 mins
6. Heat the oil in a frying pan and fry the meatballs for 2-3 mins, until they are coloured all over
7. Remove from the pan and set aside
8. Gently fry the onion in the same pan for 3-4 mins
9. You can add the meatballs and onion straight to the slow cooker without searing them first, but it’s worth the effort if you have time
10. Put the onion and meatballs in the slow cooker, then add the tomatoes, passata, red wine vinegar, sugar and rosemary
11. Cook on low for 4½ hours
12. Remove the meatballs with a slotted spoon and set aside
13. Add the spaghetti to the sauce, making sure that it’s fully submerged — you may have to break it in half, depending on the size of your slow cooker
14. Cook, covered, for a further 25 mins until the spaghetti is al dente, then return the meatballs to the slow cooker and warm through
15. Serve garnished with the basil leaves