Heat the oil in a casserole dish, then brown the chicken pieces all over. Transfer them to a plate.
Meanwhile, cut the chorizo into small cubes. Thinly slice the onion and garlic. Peel and dice the sweet potatoes and red pepper.
Add the chorizo and onion to the pan and cook for 5 minutes, until the onion has softened and the chorizo has released its fat. Add the garlic, red pepper and the spices, stir for a few seconds, then add the tomatoes. Stir again for a few seconds, then add the chicken stock, passata and sweet potatoes.
Bring to the boil, then turn down the heat. Put a lid on and cook for about 35 minutes or until the veggies are tender and the chicken has cooked through properly. You might need to add more stock.
Scatter the coriander leaves on top, then serve.