Stir the milk and breadcrumbs in a bowl and let soak for 5 minutes.
Combine beef, pork, half the onion and garlic, parsley, salt, pepper, allspice, nutmeg, and the soaked crumbs. Mix gently.
Roll the mixture into 1-inch meatballs and set on a tray.
Heat the olive oil in a Dutch oven over medium-high. Brown meatballs in batches, turning to color all sides. Transfer to a plate.
Reduce heat to medium. Add remaining onion, carrots, and celery to the pot. Cook until slightly softened, about 4 minutes.
Melt the butter in the pot. Sprinkle in flour and cook, stirring, for 1 to 2 minutes to form a roux.
Slowly whisk in beef broth and Worcestershire, scraping up browned bits from the bottom.
Return the meatballs and any juices to the pot. Simmer gently for 12 to 15 minutes, until cooked through.
Stir in the egg noodles and cook until tender, about 6 to 7 minutes.
Lower the heat. Stir in heavy cream and lemon juice. Taste and adjust salt and pepper.
Ladle into bowls and finish with extra parsley if you like.