01 - Combine breadcrumbs and milk in a large bowl. Allow to soak for 5 minutes.
02 - Add ground beef, ground pork, chopped onion, minced garlic, egg, salt, pepper, allspice, and nutmeg to the soaked breadcrumbs. Mix until just combined to avoid overworking.
03 - Shape the mixture into walnut-sized balls, each about 1 1/4 inches in diameter.
04 - Heat butter and oil in a large skillet over medium heat. Cook meatballs in batches, turning to brown them on all sides, about 8 minutes per batch. Remove and place on a plate.
05 - Melt butter in the same skillet. Whisk in flour and cook for 1 minute, stirring constantly.
06 - Gradually add beef or vegetable stock while whisking to prevent lumps. Stir in heavy cream, soy sauce, and Dijon mustard. Simmer until the sauce thickens, 5 to 7 minutes.
07 - Return the browned meatballs to the skillet, coating them in the sauce. Simmer gently for 5 to 10 minutes, until heated through.
08 - Present hot, ideally accompanied by mashed potatoes, lingonberry jam, and steamed vegetables.