1Heat the oven to 400 F and line a baking sheet with foil.
2Soak the breadcrumbs in the milk for 5 minutes until soft, then mash into a paste.
3In a large bowl, combine the beef, pork, egg, breadcrumb paste, grated parmesan, half the minced garlic, the parsley, oregano, 1 teaspoon salt and a generous grind of pepper. Mix gently with your hands just until combined.
4Roll the mixture into about 16 meatballs, roughly 1.5 inches across, and set them on the baking sheet. Bake 15 to 18 minutes until browned and cooked through.
5While the meatballs bake, warm 2 tablespoons olive oil in a dutch oven over medium heat. Add the diced onion with a pinch of salt and cook 6 minutes until soft.
6Add the remaining garlic and the red pepper flakes and cook 1 minute until fragrant.
7Pour in the crushed tomatoes, season with salt and pepper, and simmer gently 15 minutes, stirring now and then.
8Bring a large pot of well salted water to a boil and cook the spaghetti until just al dente. Reserve 1 cup of the pasta water, then drain.
9Nestle the baked meatballs into the sauce, cover, and simmer 5 minutes so they absorb flavor. Stir in the torn basil.
10Toss the spaghetti with a splash of pasta water and the remaining tablespoon of olive oil, then serve topped with sauce, meatballs and extra parmesan.