In skillet heat half the oil and half the butter and saute onion until golden. Place in bowl. Add bread crumbs, 1/2 cup water, egg yolks, garlic, salt, oregano and parsley.Mix well. Add ground beef and mix well again. Let stand 30 minutes to blend flavors. Form into one inch balls for appetizers or three inch ovals for entree. In same skillet heat remaining oil and butter and saute meatballs, turning to brown all sides. Transfer to serving dish.Pour lemon juice or red wine into skillet. Bring to a boil and scrape drippings.Pour over meatballs. Grind on coarse black pepper.Sprinkle lightly with fresh minced oregano.Note: often chopped fresh mint or fresh spinach is added to the meatballs mixture.