Step 1: Place the beef mince into a large bowl. Coarsely grate half of the onion and 2 garlic cloves into the bowl. Add 1 teaspoon of oregano, breadcrumbs, and plenty of seasoning. Crack in the egg. Using your hands, thoroughly mix the ingredients with the meat until evenly combined. Shape the mixture into 20 small meatballs. Arrange them in a roasting tin and place in the fridge to chill while you prepare the soup.
Step 2: Finely chop the remaining half of the onion, carrots, and celery. Heat your largest saucepan over medium heat. Add 2 tablespoons of olive oil to the pan, then add the chopped vegetables along with a pinch of salt. Cook, stirring occasionally, until the vegetables are soft.
Step 3: Meanwhile, finely chop the remaining 3 garlic cloves and remove the rind from the Parmesan. Add the chopped garlic, the remaining 2 teaspoons of dried oregano, and the chili flakes to the saucepan. Cook for an additional minute. Then, pour in the plum tomatoes, add the Parmesan rind, and pour in the stock. Bring the soup to a boil, using the back of your spoon to break down the tomatoes. Let it simmer for 10 minutes.
Step 4: Preheat the oven to 200°C.
Step 5: Brush the chilled meatballs with 1 tablespoon of olive oil. Bake in the preheated oven for 12–15 minutes, or until cooked through and browned.
Step 6: While the meatballs are baking, add the macaroni to the soup and cook it for 1 minute less than the time stated on the package. Once the pasta is cooked, stir in the spinach until it wilts. Season the soup to taste.
Step 7: As the pasta cooks, prepare the salsa verde. Roughly chop the parsley (including the stalks) and add it to a mini food processor along with the capers, lemon juice, and the remaining tablespoon of olive oil. Add a tablespoon of water and blend until you have a rough sauce. Season to taste with salt.
Step 8: Divide the soup among four bowls, placing five meatballs in each. Add a spoonful of salsa verde to each bowl and finish by finely grating Parmesan over the top before serving.