01 - Combine breadcrumbs and milk in a large bowl and let stand for 5 minutes to fully absorb.
02 - Add ground beef, ground pork, finely chopped onion, minced garlic, egg, salt, black pepper, allspice, and nutmeg. Mix until incorporated, avoiding over-mixing to maintain tenderness.
03 - Form the mixture into small balls, about 1 1/4 inches in diameter, ensuring they are equal in size for even cooking.
04 - Heat butter and vegetable oil in a large skillet over medium heat. Fry the meatballs in batches, turning regularly, until browned on all sides, approximately 8 minutes per batch. Remove and set aside.
05 - In the same skillet, melt butter over medium heat. Add flour, whisking constantly, and cook for 1 minute to form a roux.
06 - Gradually add beef or vegetable stock while whisking to prevent lumps. Incorporate heavy cream, soy sauce, and Dijon mustard. Simmer until the sauce thickens, about 5–7 minutes. Season with salt and pepper to taste.
07 - Return the browned meatballs to the skillet, coating thoroughly with the cream sauce. Simmer gently for 5–10 minutes until the meatballs are heated through and flavors meld.
08 - Serve hot with mashed potatoes, lingonberry jam, and steamed vegetables for an authentic Swedish accompaniment.