In a large dutch oven sauté the butternut squash with 2 tablespoons of ghee for 15 minutes or until lightly golden brown. Remove from the pan and set aside.
To the same pot add 2 additional tablespoons of ghee and saute the onions for 10 minutes. Add the chicken pieces and turmeric and continue to saute for 10 minutes. Be sure to rotate the chicken so that it can be lightly browned on both sides.
Add the hot water, cover and reduce the flame, and cook the chicken for 30 minutes.
Add the butternut squash, cinnamon, salt, pepper, sugar, lime juice, and golden plums, continue to cook covered for another 30-40 minutes, or until the chicken is tender.
While the stew is simmering, gently saute the walnuts with 1 tablespoon of ghee in a small frying pan for 2 minutes. Remove from heat and set aside.
Once the chicken is tender, pour in the saffron water and gently stir and remove from the heat. Allow the stew to rest for 5 minutes before transferring to a serving platter.
Sprinkle the walnuts over the top and serve hot with Persian steamed basmati rice or Persian flatbreads.