If you can an ovenproof pan or Dutch oven the entire recipe can be made in there. Otherwise, begin by cooking the onions in a frying pan and transfer them to a casserole dish for the remainder of the recipe.
Heat butter in a skillet or ovenproof dish on medium heat.
Add onions and carrots, season with a pinch of salt and saute for 5-7 minutes until tender and onions are translucent. Once cooked, add minced garlic and cook for another 1 minute until fragrant.
While onions are cooking, add chicken thighs to a large bowl and drizzle with a little olive oil and sprinkle with spices. Using your hands, rub the spices onto the chicken until well covered.
Once the onions are done cooking, add coriander and cumin and stir well to combine. (If you cooked the onions in a frying pan, transfer them to a casserole dish now.) Pour in rice, peas, cover with broth and give it a stir to ensure onion mixture, spices and rice is well combined in the broth. Drop the cinnamon stick into the broth.
Place the chicken thighs in the pot or casserole dish leaving room in between. They will be slightly submerged in the broth mixture which is fine, this will help to add moisture as they cook.
Cover casserole dish with aluminium foil, or if using ovenproof pot cover with lid, and transfer to the oven for 50 minutes. Remove the foil or lid and bake for an additional 10 minutes.
Remove from oven and allow to stand for 5 minutes. Remove chicken to fluff rice with a fork before serving.
For extra crispy chicken skin you can return the chicken thighs to the oven on broil for an additional 5 minutes.