In a large mixing bowl, combine ground beef, ground pork, breadcrumbs, egg, milk, Parmesan, garlic, parsley, oregano, salt and pepper. Mix gently using your hands until evenly combined. Avoid overworking the mixture, which can toughen the meatballs.
Scoop out roughly 2 tablespoons of the mixture and roll into balls about the size of a golf ball. Place them on a baking tray lined with parchment. You should have 12 to 14 meatballs. Cover and refrigerate for 15 minutes to help them hold their shape.
Heat a large pan over medium heat with a splash of oil. Brown the meatballs in batches, turning to sear all sides. Cook only until golden on the outside. Do not crowd the pan. Transfer the browned meatballs to a plate and set aside.
In the same pan, lower the heat and add olive oil, then sauté the onion until soft and translucent, about 5 minutes. Stir in garlic and cook briefly until fragrant, around 30 seconds.
Add tomato paste and cook for 1 minute to deepen the flavour. Pour in crushed tomatoes, sugar, dried basil, and season with salt and pepper. Stir well and bring to a gentle simmer.
Return the browned meatballs to the sauce. Cover and let simmer over low heat for 25 to 30 minutes. The meatballs should be fully cooked through and infused with sauce. Stir occasionally to prevent sticking.
While the sauce simmers, bring a large pot of salted water to a boil. Add spaghetti and cook according to packet instructions until al dente. Reserve 120ml of pasta water before draining.
Toss drained spaghetti with a few ladles of tomato sauce and a splash of the reserved pasta water if needed to loosen. This helps the sauce cling to the pasta beautifully.
Plate the spaghetti and top with generous helpings of meatballs and extra sauce. Sprinkle with grated Parmesan and freshly torn basil or parsley. Drizzle with a touch of good olive oil if desired.
Serve hot with crusty bread or a simple green salad. For a polished touch, use warmed plates and a final dusting of Parmesan. The contrast of tender meat, bright sauce and pasta texture offers the full experience of this beloved classic.