01 - In a large bowl, combine breadcrumbs and milk. Allow mixture to stand for 5 minutes until softened.
02 - Add ground beef, ground pork, onion, garlic, egg, salt, pepper, allspice, and nutmeg to the bowl. Mix gently until ingredients are just combined.
03 - Form mixture into small, evenly-sized balls about 1 1/4 inches in diameter.
04 - Heat butter and oil in a large skillet over medium heat. Working in batches, fry meatballs until browned on all sides, about 8 minutes. Transfer meatballs to a plate and set aside.
05 - In the same skillet, melt butter over medium heat. Whisk in flour and cook for 1 minute, stirring constantly.
06 - Gradually whisk in stock to avoid lumps. Stir in heavy cream, soy sauce, and Dijon mustard. Simmer until sauce thickens, about 5 to 7 minutes. Season with salt and pepper to taste.
07 - Return meatballs to the skillet, coating them well with sauce. Simmer gently for 5 to 10 minutes, until warmed through.
08 - Serve meatballs and sauce hot with mashed potatoes, lingonberry jam, and steamed vegetables if desired.