In a large mixing bowl, combine ground beef, ground pork, and bread crumbs. Set the meat mixture aside.
In a medium skillet, cook onion in the 2 tablespoons butter until tender, but not brown. Add to meat mixture, along with parsley. In a food processor bowl or food grinder, process or grind mixture. (If you have a small food processor bowl, process half at a time.) Return to mixing bowl. Add egg, lemon peel, salt, basil, and pepper; mix well.
Shape meat mixture into nine 1/2-inch-thick patties. Coat the patties with the flour.
In a large skillet, melt 1 tablespoon of the butter. Cook 3 or 4 patties, uncovered, over medium-low heat for 12 to 15 minutes or until done (160 degree F); turn once. Repeat with remaining butter and patties. Makes 9 servings.
You can wrap and freeze uncooked, shaped patties for several months. Thaw in your refrigerator before cooking.