Combine the fresh breadcrumbs and whole milk in a large bowl. Let the mixture stand for 5 minutes, until the breadcrumbs have absorbed the milk and formed a soft panade.
Add the Parmesan cheese, ricotta cheese, parsley, garlic, Italian seasoning, salt, and black pepper to the panade and stir until evenly combined.
Add the ground beef and ground pork. Mix gently just until the seasonings are distributed, taking care not to overwork the meat or the finished meatballs can become firm.
Shape the mixture into about 20 meatballs, each approximately 1 1/2 inches across. Place them on a tray while the skillet heats.
Heat the olive oil in a large skillet over medium-high heat. Brown the meatballs in batches, turning as needed, until a golden crust develops on several sides.
Pour the marinara sauce into a wide saucepan and bring it to a gentle simmer. Add the browned meatballs, cover partially, and simmer for 18 to 22 minutes, until cooked through and exceptionally tender.
Let the meatballs rest in the sauce for 5 minutes before serving so they absorb additional flavor while remaining juicy.
