In a large bowl, combine ground beef and pork.
Add breadcrumbs, Parmesan cheese, onion, milk, egg, salt, pepper, allspice, and nutmeg.
Mix until well combined, then form into small meatballs.
Heat butter in a skillet over medium heat.
Brown the meatballs on all sides, about 5-7 minutes.
Remove the meatballs and set aside.
Add flour to the skillet, stirring to combine with the drippings.
Gradually whisk in the beef broth, cooking until thickened.
Stir in the heavy cream and return the meatballs to the skillet.
Simmer for an additional 10 minutes until meatballs are cooked through.