01 - In a large bowl, stir together breadcrumbs and milk and allow to stand for 5 minutes.
02 - Add ground beef, ground pork, onion, garlic, egg, salt, black pepper, allspice, and nutmeg to the breadcrumb mixture. Mix gently until the ingredients are just incorporated.
03 - Shape the mixture into small balls, about the size of a walnut (approximately 1 1/4 inches in diameter).
04 - Heat butter and oil in a large skillet over medium heat. Fry the meatballs in batches, turning occasionally, until browned on all sides, about 8 minutes total. Remove meatballs from skillet and set aside.
05 - Melt butter in the same skillet. Add flour and whisk continuously for 1 minute to cook the flour.
06 - Gradually whisk in beef or vegetable stock to avoid lumps. Stir in heavy cream, soy sauce, and Dijon mustard. Bring to a simmer and cook until the sauce thickens, about 5 to 7 minutes.
07 - Return meatballs to skillet and toss to coat with the sauce. Simmer gently for 5 to 10 minutes until meatballs are warmed through.
08 - Plate meatballs hot with cream sauce. Traditionally accompanied by mashed potatoes, lingonberry jam, and steamed vegetables.