Prepare the Meatball Mixture: In a small bowl, combine the breadcrumbs and milk. Let them sit for 5 minutes to soak. In a larger mixing bowl, add the beef and pork mince, soaked breadcrumbs, grated Parmesan, beaten egg, minced garlic, parsley, salt, and pepper. Mix gently with your hands until just combined. Be careful not to overwork the mixture, as this can make the meatballs tough.

Form and Brown the Meatballs: Roll the mixture into 16 evenly sized meatballs (about the size of a golf ball). Heat the olive oil in a large, heavy-based frying pan or skillet over a medium-high heat. Add the meatballs to the pan. What works best for me is browning them in two batches to avoid overcrowding. Cook for 5-7 minutes, turning occasionally, until they are nicely browned on all sides. Remove them with a slotted spoon and set aside.

Start the Sauce: Reduce the heat to medium. Add the finely chopped onion to the same pan, using the leftover fat from the meatballs. Cook for 5-6 minutes until soft and translucent. Add the minced garlic and cook for another minute until fragrant.

Simmer the Sauce: Pour the tinned tomatoes into the pan, crushing them with the back of a wooden spoon. Stir in the tomato purée, dried oregano, and sugar. Season with salt and pepper. Bring the sauce to a gentle simmer.

Cook the Meatballs in the Sauce: Carefully return the browned meatballs to the pan, nestling them into the sauce. Reduce the heat to low, cover, and let them simmer gently for 20-25 minutes. This allows the meatballs to cook through and absorb the flavours of the sauce.

Finish the Sauce: After 20 minutes, remove the lid and stir in the torn fresh basil leaves. Let it bubble for another 5 minutes to thicken slightly if needed.

Prepare the Subs: While the meatballs are finishing, preheat your grill to a medium-high setting. Slice the sub rolls horizontally, but not all the way through, so they open like a book. Place them on a baking tray and lightly toast them under the grill for 1-2 minutes until just golden.

Assemble and Grill: Spoon 4 meatballs and a generous amount of sauce into each toasted roll. Top with a good handful of grated mozzarella. Place the assembled subs back on the baking tray and pop them under the grill for 3-4 minutes, or until the cheese is completely melted, bubbling, and starting to turn golden brown. Serve immediately while hot and messy!