Heat the oil in a large sauté pan or casserole and brown the chicken on all sides. You may need to do this in batches. Once brown remove from the pan and set aside.
Reduce the heat and add the onion to the pan cook, stirring until softened and beginning to colour about 5 minutes
Stir in the tomato puree and curry paste and cook gently for 1 minute. Then stir in the flour and cook for another minute.
Gradually stir in the stock. Return the chicken to the pan and add the remaining ingredients. Bring to the boil, then reduce the heat cover and simmer over a low heat for 1 hour.