1. If you are using currants, skip this step. Combine the sugar and water in a small saucepan and heat over medium until the sugar has dissolved. Remove the saucepan from the heat and add the barberries. Allow the barberries to soak while you prepare the rest of the recipe.
2. Heat 2 tablespoons of olive oil in a sauté pan. Add the onion and cook for 10-15 minutes, stirring occasionally, until it is golden and caramelized. Transfer onion to a small bowl.
3. Combine the chicken with salt, pepper, 2 tablespoons of olive oil, cardamom pods, cloves and cinnamon. Mix everything together with your hands.
4. Heat a large dutch oven over medium-high. Add the chicken, along with the spices, to the pot and cook for 5 minutes on each side. You want it to get golden, and for the skin to crisp up a bit. Use a pair of tongs to remove the chicken from the pot and set aside.
5. Add the rice, caramelized onion, salt, and pepper to the dutch oven. Stir until the rice is coated in the oil/leftover chicken fat. Drain the barberries and add them to the pot. If you are using currents, add them in at this stage. Stir and then re-add the chicken to the pot, tucking it into the rice.
6. Add the boiling water, cover, and dial down the heat to low. Continue cooking, over very low heat, for 30 minutes.
7. After 30 minutes, remove the pan from the heat, take off the lid and place a tea towel over the pot. Replace the lid and let sit for 10 minutes. Meanwhile, use a spoon to stir the olive oil into the yogurt and set aside.
8. Stir in the herbs and use a fork to fluff the rice. Season with more salt and pepper, if desired. Transfer to a serving bowl.
Enjoy this dish hot or warm, with a few dollops of yogurt sauce.