01 - Combine the breadcrumbs and milk in a large mixing bowl and let stand for 5 minutes until softened.
02 - Add ground beef, ground pork, onion, garlic, egg, salt, black pepper, allspice, and nutmeg to the soaked breadcrumbs. Gently mix by hand or with a wooden spoon just until combined, ensuring the mixture does not become dense.
03 - Roll the meat mixture into small balls, each about the size of a walnut or roughly 1 1/4 inches in diameter, and set aside on a tray.
04 - Heat unsalted butter and vegetable oil in a large skillet over medium heat. Fry meatballs in batches, turning frequently, until evenly browned on all sides, about 8 minutes per batch. Transfer browned meatballs to a plate.
05 - Melt butter in the same skillet over medium heat. Whisk in flour and cook, stirring constantly, for about 1 minute to form a light roux.
06 - Gradually pour in beef or vegetable stock, whisking continuously to prevent lumps. Stir in heavy cream, soy sauce, Dijon mustard, salt, and pepper. Allow to simmer until the sauce thickens, approximately 5 to 7 minutes.
07 - Return browned meatballs to the skillet, coating them with the sauce. Simmer gently for 5 to 10 minutes until meatballs are cooked through and heated evenly.
08 - Serve the meatballs hot, generously glazed with the creamy sauce. Accompany with mashed potatoes, lingonberry jam, and steamed vegetables for an authentic presentation.