Sprinkle ground saffron on ice cubes and let it melt at room temperature.
Clean the chicken and pat dry it completely, on the skin and in the cavity. Run your fingers under the skin to make sure it’s separated from the meat. But don’t tear it. This is to make sure the saffron flavor can get under the skin as well.
Mix bloomed saffron, olive oil, melted butter and the juice of 1/2 lemon in a bowl and using a small spoon, slowly pour it under the skin. Massage the skin to make sure the saffron and oil are getting all over the meat.
Place the head of garlic in the cavity. Cross the legs and tie them using a kitchen twine. Place the chicken in a roasting pan, pour in the chicken stock, and roast for about 1 hour and 20 minutes until the thighs register at 165°F. Baste the chicken only once halfway through.
Once the chicken is cooked, let it sit for 10 minutes before carving. Serve saffron chicken with barberry rice.
While the chicken is roasting, make the rice. Place the rice, water, salt, and 2 tablespoons oil in a large saucepan or a pot and bring to a boil. Turn the heat to low and let it simmer until the water is almost evaporated. Using a fork, bring the rice to the middle to form a mountain shape. Add the remaining 2 tablespoons oil around the edges. Wrap the lid in a clean kitchen towel and place it on top of the pot. Let the rice cook for another 10 to 12 minutes until fully cooked. Take 1/2 cup of the cooked rice and mix it with bloomed saffron. Set aside.
Wash and dry the barberries. In a small pan, heat the 1 tablespoon vegetable oil over medium low heat and add the barberries to the pan. Stir constantly and add the salt and sugar. Sauté for about 3 to 5 minutes over medium-low to low.
Transfer the white rice into serving plates and top them with some saffron rice and sautéed barberries. Serve with saffron roast chicken.