In a large mixing bowl, combine ground beef, ground pork, breadcrumbs, milk, chopped onion, minced garlic, egg, allspice, nutmeg, salt, and pepper. Mix until well combined.
Shape the meat mixture into small meatballs, about 1-1.5 inches in diameter.
Heat vegetable oil in a large skillet over medium heat. Add the meatballs and cook until browned on all sides and cooked through. Remove the cooked meatballs from the skillet and set aside.
In the same skillet, melt butter over medium heat. Whisk in flour to create a roux and cook for a minute, stirring constantly.
Gradually pour in the broth, stirring continuously to prevent lumps from forming.
Stir in the heavy cream or sour cream and continue cooking until the sauce thickens and reaches a creamy consistency.
Season the sauce with salt and pepper to taste.
Return the cooked meatballs to the skillet and simmer in the sauce for a few minutes, allowing the flavors to meld together.
Serve the Swedish Meatballs hot, garnished with fresh parsley. Accompany them with lingonberry jam or cranberry sauce on the side.
