In a large bowl, combine the ground beef, ground pork, breadcrumbs, milk, egg, salt, black pepper, allspice, and nutmeg. Mix well with your hands.
Shape the mixture into small balls, about 1 inch in diameter.
In a large skillet, melt the butter over medium heat. Add the meatballs and cook for about 10 minutes, turning occasionally, until browned on all sides.
Remove the meatballs from the skillet and set aside. Add the flour to the skillet and whisk until smooth.
Gradually stir in the beef broth and lingonberry jam. Bring to a boil, stirring constantly, until the sauce thickens.
Reduce the heat to low and add the heavy cream. Stir until well combined.
Return the meatballs to the skillet and simmer for an additional 10-15 minutes, until the sauce is heated through and the meatballs are fully cooked.
Serve hot with lingonberry sauce on top.