Melt 2 Tablespoons unsalted butter in a 12-inch skillet over medium low to medium heat. Add the onions and cook for about 15 minutes until very tender, but not browned. Remove from heat and allow to to cool.
Add the cooked and cooled onions, ground turkey, 2 Tablespoons softened unsalted butter, seasonings, bread crumbs, and egg to the bowl of a food processor fitted with a steel blade. Process for 20 seconds; scrape down the sides and process for an additional 10 second, or until the mixture is well combined. Cover with plastic wrap and refrigerate until ready to use.
Preheat oven to 350° F.
Place 1/2 cup of all purpose flour on a large plate. Roll the turkey mixture into 1-inch meatballs. Just before browning, roll the meatballs lightly in the flour; shake off the excess flour.
Place 1 Tablespoon each of butter and vegetable oil in a large skillet and set over medium high heat. When the butter foam begins to subside, add the meatballs, taking care not to crowd them. Cook until browned, about 5 minutes. Drain on paper towels. Repeat with remaining meatballs.
Place the browned meatballs on a large baking sheet lined with non-stick aluminum foil. Bake at 350º F for 20 minutes, or until meatballs are fully cooked.
Meanwhile, add grape jelly and chili sauce to a large saucepan. Cook over medium heat for 10 minutes, or until jelly is fully melted. Add cooked meatballs. Stir carefully with wooden spoon to thoroughly coat meatballs. Cook for 10 minutes, or until meatballs are thoroughly heated. (Note: Can be refrigerated at this point, and served later. This glaze is also excellent with little smokies.)
Yield: 48 meatballs; 10 to 12 servings.