Mix together the ground beef and pork, with the milk, breadcrumbs, egg, onion, salt, pepper, and allspice. Let sit for 20 minutes.
Heat a cast iron skillet. Add oil and 1 tablespoon butter. When hot, form the meatballs and add them to the skillet, not touching each other. Cook, turning occasionally, until well browned and cooked through. Remove from skillet.
Add remaining butter to the skillet, along with the flour. Whisk together and cook the flour for 1 minute.
Slowly add the beef stock, whisking constantly, until stock is fully incorporated. Turn the heat down. Add the cream, soy sauce, pepper, and apple sauce. Whisk and cook for an additional 1 minute.
Serve the meatballs with sauce served over the top. Mashed potatoes and lingonberry jam should also be served alongside the meatballs.