Step 1Place the lamb in a large saucepan and cover it with water. Bring to a boil, then reduce the heat to low and simmer the lamb until it reaches 130 degrees, about 1 1/2 hours. Remove it from the water and grind it 1 minute in the food processor. Knead through the meat with your fingers and remove all tendons. Return the meat to the processor, add the pistachios, cinnamon, pepper, salt, parsley, mint, celery leaves and egg, and process until smooth, 2 minutes.
Step 2Form the mixture into 8 patties. Fry the patties in the oil over medium heat until they're browned, about 3 minutes a side.