Remove the skin from chicken pieces. Marinate chicken in grated onions, salt and pepper for 4-5 hours.
Cook rice using the recipe given for polow or kateh.
Wash barberries twice with cold water and drain the water. Add sugar and fry in butter over medium heat for about five minutes.
Pour saffron in a small bowl. Pour in 2-3 spoons of hot water and mix. Fill the bowl with rice and mix well. Add saffron-rice and barberries to the rest of the rice and mix well.
Cook chicken under grill for 15-20 minutes turning each piece a few times during cooking. Serve with barberry-rice.