Heat 1 tbsp of oil in a casserole dish. Add the chicken and cook until lightly browned all over. You may have to do this in batches. Remove the chicken from the pan and set aside. Pour in the remaining oil and cook the onion for 5 minutes until softened. Then add the garlic, ginger and chilli and cook for another 2 minutes. Stir in the cumin and the ground coriander and cook for a minute more and then add the tomatoes. Simmer for 10 minutes, topping up with a little water if needed.
Stir the peanut butter into the sauce until smooth, then return the chicken to the pan and cook for 5-10 minutes more until the meat is cooked through. Scatter over the coriander and peanuts and serve with some plain boiled rice, if you like.