Divide the chicken into 2 x breast and wing, 2 x thigh and drumstick.
Toss the chicken pieces with onions, olive oil, ginger, cinnamon, saffron, lemon juice, water, 2 tsp salt, and a good sprinkle of freshly ground black pepper in a large bowl.
Let them marinate for at least 1 hour or overnight in the refrigerator.
Preheat the oven to 210°. Spread the hazelnuts out on a baking sheet, and roast them in the oven for 10 minutes until they're lightly colored.
Then coarsely chop them and set aside.
Transfer the chicken and marinade to a baking dish large enough to hold everything in a single layer.
Place the chicken pieces skin-side up and roast in the oven for about 35 minutes.
Meanwhile, mix honey, rose water, and nuts together.
Take the chicken pieces out of the oven, spoon the nut syrup over them, spreading it evenly to coat the meat.
Return the baking dish to the oven and roast the chicken for another 5-10 minutes until the chicken is fully cooked and the nuts are golden brown.
Arrange the chicken pieces on a platter and, if desired, garnish with the chopped scallions.