Light and Fluffy Meatballs

Name: Light and Fluffy Meatballs
Ingredients: 2 tablespoons extra-virgin olive oil; 1 small yellow onion, finely chopped; 5 slices white bread, crusts removed and torn into pieces (about 3 cups); 1 cup whole milk; 1 pound ground chuck beef; 1 pound ground pork; 1 pound ground veal; 1 pound whole-milk ricotta; ½ cup grated Parmesan cheese, plus more for garnish; ⅓ cup chopped flat leaf parsley; 1 tablespoon chopped oregano; 2 teaspoons salt; ½ teaspoon ground black pepper; 2 quarts Basic Italian Tomato Sauce , or other Italian tomato sauce