In a mixing bowl, combine all the ingredients for the meatballs together and form 12 balls. Place an oven proof pan over a medium heat and add the garlic oil. Fry the meatballs for about 5-8 minutes, turning them regularly so they are well coloured - they don't need to be fully cooked in the middle at this point. Remove from the pan (no need to clean the pan).
Add the leek to the pan and cook until lightly browned. Add in the passata, tomato puree, dried mixed herbs, sugar, salt, pepper and boiling water. Mix together, then add in the dry spaghetti. As it starts to soften, separate it as best you can and push it deeper into the sauce so it doesn’t clump together. Pop a lid on for 5 minutes if you have one.
After 5 minutes and once your pasta is softened, add in the meatballs again. Continue to cook for a further 5 minutes until the pasta is fully cooked and the sauce has thickened to your liking. At this point you could simply serve and enjoy, or for a cheesy 'al forno' finish, follow the last step.
For a cheesy layer, top with grated cheese. Pop under the grill at a medium heat for 4-5 minutes until the cheese is melted and golden.