Spaghetti and Meatballs Recipe

Name: Spaghetti and Meatballs Recipe
Ingredients: 2 1/2 ounces (75g) fresh, crustless white bread, cut into 1/2-inch cubes (about 2 unpacked cups); 1/2 cup (120ml) whole milk; 1 medium (8-ounce; 225g) yellow onion, minced; 6 medium cloves garlic (about 1 ounce; 30g), finely minced; 1 1/2 ounces (45g) Parmigiano-Reggiano, grated; 3 ounces (85g) pancetta, finely minced; 3 large egg yolks; 1/3 cup loosely packed fresh parsley leaves and tender stems (3/4 ounce; 20g), minced; 2 teaspoons Diamond Crystal kosher salt (8g); for table salt use half as much by volume or the same weight; 1/2 teaspoon freshly ground black pepper; 3/4 teaspoon dried oregano; 3/4 teaspoon ground fennel seed; 1 pound (450g) ground beef (at least 25% fat; see note); 1/2 pound (225g) ground pork (at least 25% fat; see note); 3 tablespoons (45ml) extra-virgin olive oil; 2 quarts (2L) tomato sauce, such as Quick and Easy Italian-American Red Sauce; 1 pound (450g) spaghetti; Kosher salt; 2 ounces (55g) finely grated Parmigiano-Reggiano, plus more for sprinkling