Place the basmati rice in a bowl of cold water and soak for 30 minutes. Drain and rinse under cold water until the water runs clear, then set aside.
Preheat the oven to 160°C (320°F).
Heat 3 tablespoons olive oil in a 30cm ovenproof casserole over medium heat. Add the chicken pieces and sauté until golden brown on all sides, then transfer the chicken to a plate and set aside.
Reduce heat to low, add the butter to the pan, then add the chopped onion, grated carrot, cinnamon stick, star anise and thyme stalks. Cook, covered for most of the time, until the onions are translucent, about 5 minutes.
Add the ground cumin, turmeric, smoked paprika, chilli flakes and crushed garlic and cook for about 1 minute until fragrant.
Pour in the 1/2 cup fresh orange juice to deglaze the pan, scraping up any browned bits. Stir in the orange marmalade and cook until most of the liquid has evaporated.
Add the drained rice to the pan and toss to coat in the oil and spices for about 1 minute.
Pour in the hot chicken stock and add the orange zest. Increase the heat to medium-high and bring to a rolling boil; cook for exactly 2 minutes after it starts boiling.
Return the browned chicken to the casserole and gently toss to distribute evenly. Cover with a lid and transfer the casserole to the preheated oven. Bake for 25 minutes.
Remove from the oven and let the pilaf rest, covered, for 5 minutes. Remove the cinnamon, star anise pods and thyme stalks, fluff the rice with a fork, then scatter chopped parsley and toasted nuts if using. Serve hot.