01 - Combine breadcrumbs and milk in a large bowl; allow to soak for 5 minutes.
02 - Add ground beef, ground pork, onion, garlic, egg, salt, pepper, allspice, and nutmeg to the soaked breadcrumbs. Mix gently until just incorporated.
03 - Shape mixture into small balls about 1 1/4 inch in diameter, roughly the size of a walnut.
04 - Heat butter and oil in a large skillet over medium heat. Fry meatballs in batches, turning occasionally, until browned on all sides, about 8 minutes. Set aside.
05 - In the same skillet, melt butter over medium heat. Whisk in flour and cook, stirring constantly, for 1 minute.
06 - Gradually add stock, whisking to prevent lumps. Stir in heavy cream, soy sauce, and mustard. Simmer until thickened, about 5–7 minutes. Season to taste with salt and pepper.
07 - Return browned meatballs to the skillet, coating with the sauce. Simmer gently for 5–10 minutes until heated through.
08 - Present hot, ideally alongside mashed potatoes, lingonberry jam, and steamed vegetables.