1.Heat 3 tablespoons of the oil in a large pan over a low to medium heat. Add the chopped onion and fry until softened.
2.Add the garlic, ginger, chopped chillies, chopped tomatoes and the contents of your Spice Bag the salt and sugar, then stir-fry for 3-4 minutes taking care not to let the spices burn.
3.Then add the diced chicken and cook for 5 minutes, turning the chicken regularly ensuring that it is coated in the spices. Pour over the 200ml of water, stir in the yoghurt and reduce the heat slightly so that the sauce simmers. Continue cooking, stirring occasionally, until the sauce has reduced by about a third and the chicken is cooked.
4.Mix the cornflour with the tablespoon of water to form a smooth paste and stir the cornflour mixture into the curry and leave to simmer until the sauce thickens, stirring frequently.
5.Whilst the sauce is simmering, heat the remaining tablespoon of oil in a clean pan and stir-fry the onion and green pepper over a medium to high heat for 3-4 minutes until lightly browned. Add the quartered tomatoes and fry for 2-3 minutes more, stirring until the vegetables are just tender. Add the butter and the lemon juice to the pan.
6.Reduce the heat of the curry and add the hotstir-fried vegetables and combine gently with the curry. Add the chopped coriander, sliced red chillies and serve immediately.
The heat in this dish can be controlled by the amount and type of chillies used