01 - In a large bowl, combine breadcrumbs with milk and allow the mixture to stand for 5 minutes.
02 - Add ground beef, ground pork, chopped onion, minced garlic, egg, salt, black pepper, allspice, and nutmeg to the soaked breadcrumbs. Mix gently until just combined to maintain tenderness.
03 - Form the mixture into small balls, about walnut-sized, approximately 1.25 inches in diameter.
04 - Heat butter and oil in a large skillet over medium heat. Working in batches, fry the meatballs until browned on all sides, about 8 minutes per batch. Remove and set aside.
05 - Melt butter in the same skillet. Whisk in the flour and cook for 1 minute until lightly golden.
06 - Gradually whisk in beef or vegetable stock. Stir in heavy cream, soy sauce, and Dijon mustard. Simmer until the sauce thickens, about 5 to 7 minutes.
07 - Return the browned meatballs to the skillet. Coat with sauce and simmer gently for 5 to 10 minutes until the meatballs are heated through.
08 - Serve the meatballs hot accompanied by the creamy sauce, ideally with mashed potatoes, lingonberry jam, and steamed vegetables.