01 - In a large bowl, combine breadcrumbs and milk. Allow to soak until mixture is softened, about 5 minutes.
02 - Add ground beef, ground pork, chopped onion, minced garlic, egg, salt, black pepper, allspice, and nutmeg to the breadcrumb mixture. Mix gently until just combined; do not overwork.
03 - Form the mixture into small balls, about 1.25 inches in diameter (walnut-sized).
04 - Heat butter and vegetable oil in a large skillet over medium heat. Cook the meatballs in batches, turning occasionally, until golden brown on all sides, approximately 8 minutes per batch. Transfer browned meatballs to a plate.
05 - In the same skillet, melt butter over medium heat. Whisk in flour and cook for 1 minute, stirring constantly.
06 - Gradually add stock, whisking steadily to prevent lumps. Stir in heavy cream, soy sauce, and Dijon mustard. Simmer the sauce gently until it thickens, about 5 to 7 minutes.
07 - Return the browned meatballs to the skillet, tossing them in the cream sauce. Let simmer on low heat for 5 to 10 minutes, until meatballs are fully heated and coated.
08 - Serve hot, ideally accompanied by mashed potatoes, lingonberry jam, and steamed vegetables.