In a large skillet, melt butter and oil over medium heat. Add onions; cook, stirring occasionally, until they start to caramelize, about 8 to 10 minutes. Remove onions to a large mixing bowl and add beef, egg, parsley (or Italian seasoning), salt and red pepper flakes; mix well to combine. With damp hands, roll forty-eight 1/2-inch meatballs.
Place same skillet over medium-low heat. Add meatballs, broth and wine; simmer until cooked through, gently turning meatballs once during cooking, about 20 minutes. Yields 4 meatballs per serving.