Have your butcher grind beef, veal, and pork together twice. (Or buy ground beef, ground veal, and ground pork and process together in a food processor bowl or grind together in food grinder.)
In a small bowl, soak bread in milk, broth, or water. Set aside.
In a small skillet, cook onion in the 1 tablespoon butter until onion is tender. Squeeze and discard any excess milk from bread.
In a medium bowl, combine eggs, the 3 tablespoons parsley, the salt, Worcestershire, lemon peel, lemon juice, paprika, nutmeg (if you like), bread, and onion mixture. Add meat; mix well.
In a 4-1/2-quart Dutch oven, bring vegetable or beef broth to boiling. Meanwhile, with wet hands, shape meat mixture into 2-inch balls. Carefully drop into boiling broth. Return to boiling; reduce heat. Cover and simmer for 15 minutes or until thoroughly cooked.
With a slotted spoon, transfer meatballs to serving bowl; keep warm. Measure and reserve 2 cups of the stock; discard any remaining stock.*
In the Dutch oven, melt the 3 tablespoons butter. Stir in flour. Add the 2 cups reserved stock all at once. Cook and stir over medium heat until thickened and bubbly. Cook and stir for 1 minute more. Stir in the 2 tablespoons parsley. Season with salt and pepper. Serve klops and sauce over noodles or spaetzle. Serve with capers, sour cream, and anchovies, if you like. Makes 6 servings.
Instead of discarding the extra stock used for cooking, you can strain the stock and freeze it to use in soups.