Lamb or beef (precisely 20% fat, 80% meat) is minced twice for finer consistency. Salt, garlic powder, black pepper, celery powder, sumac, very finely grated onion (the extra juice is squeezed out and saved for later) and one egg yolk per pound of meat are added. All ingredients are mixed, covered, and left to marinate in the refrigerator for at least four hours or overnight.