01 - In a large bowl, combine breadcrumbs and milk. Allow to stand for about 5 minutes until breadcrumbs are softened.
02 - Add ground beef, ground pork, finely chopped onion, minced garlic, egg, salt, black pepper, allspice, and nutmeg to the soaked breadcrumbs. Gently mix until just combined, taking care not to overwork the mixture.
03 - Shape the mixture into balls roughly the size of walnuts, approximately 1 1/4 inches in diameter.
04 - Heat unsalted butter and vegetable oil in a large skillet over medium heat. Fry the meatballs in batches until they are browned on all sides, about 8 minutes per batch. Remove meatballs from the skillet and set aside.
05 - In the same skillet, melt unsalted butter over medium heat. Whisk in the all-purpose flour and cook for 1 minute, stirring constantly.
06 - Gradually pour in beef or vegetable stock while whisking to prevent lumps. 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 and gently coat them with the cream sauce. Simmer on low for 5 to 10 minutes, until the meatballs are heated through.
08 - Serve meatballs with the cream sauce while hot, ideally accompanied by mashed potatoes, lingonberry jam, and steamed vegetables.