1. Prepare the Mixture: In a large bowl, combine the pork mince, grated onion, minced garlic, beaten egg, grated Parmesan, and chopped parsley. If you're using fennel seeds or a splash of milk, now's the time to add them.
2. Season and Bind: Add the breadcrumbs to the mixture for texture. Season generously with salt and freshly ground black pepper. Using your hands, gently but thoroughly mix the ingredients until well combined.
3. Test the Mixture: Before you go all-in, it’s wise to cook a small test meatball. Heat a small pan with a bit of olive oil and cook the test meatball until it's cooked through. Taste it, and adjust your seasoning if necessary.
4. Shape the Meatballs: Wet your hands slightly to prevent sticking, and shape the mixture into golf ball-sized meatballs. Place them on a tray lined with parchment paper.
5. Brown the Meatballs: In a large frying pan, heat the olive oil over medium-high heat. Brown the meatballs in batches, turning them to get an even colour on all sides. You don't need to cook them through at this stage, just aim for a good crust.
6. Simmer in Sauce: Once all meatballs are browned, transfer them into your homemade tomato sauce. Let them simmer on low heat for about 20-30 minutes. This will not only cook the meatballs but also allow the flavours to marry with the sauce.
7. Final Touch: Just before serving, sprinkle some additional grated Parmesan and a smattering of freshly chopped parsley for garnish.
8. Serve and Enjoy: Serve your meatballs hot, ideally over a bed of al dente pasta, with plenty of your wonderful tomato sauce.

Using an air fryer like the Ninja Foodi is an excellent way to cook meatballs with a healthier twist, as it significantly reduces the amount of oil used in the cooking process. The high-speed air circulation in the appliance also ensures that the meatballs are cooked evenly, giving them a nice, crispy texture on the outside while keeping them juicy on the inside.

Adjustments and Steps for Air Frying:

1. Preheat the Air Fryer: Before you begin, preheat your air fryer to about 190°C. Preheating ensures that the cooking chamber is at the right temperature for even cooking.
2. Shape the Meatballs: As per the original recipe, shape your pork mince mixture into golf ball-sized meatballs. Because air fryers cook through circulating hot air, you don't need to worry too much about flattening the meatballs for even cooking.
3. Prepare the Basket: Lightly spray or brush the air fryer basket with olive oil to prevent sticking. You could also use a piece of parchment paper at the bottom if your air fryer allows it (just make sure it doesn't obstruct the air circulation).
4. Place the Meatballs: Arrange the meatballs in a single layer in the basket, making sure there is some space between each to allow for good air circulation.
5. Cooking Time: Cook the meatballs at 190°C for about 12-15 minutes. The exact time might vary depending on the size of your meatballs and the specific model of your air fryer. Halfway through the cooking time, pause the air fryer and turn the meatballs to ensure even cooking and browning.
6. Check for Doneness: Use a meat thermometer to confirm that the internal temperature of the meatballs has reached at least 74°C, which is the safe temperature for minced pork.
7. Finish in Sauce: To allow the meatballs to absorb the flavours of your tomato sauce, transfer them from the air fryer to your sauce pot and simmer them together for an additional 10-15 minutes.
8. Garnish and Serve: As with the stovetop version, a sprinkle of Parmesan and a dash of fresh parsley will elevate your dish to perfection.

Air frying is a splendidly efficient way to get a healthier, flavour-packed meatball dish. It's especially useful for those busy weekdays when you want something delicious without the added fuss or calories.