Chop each chicken thigh into 6 pieces and mix in a bowl with the yoghurt, garam masala, turmeric and cayenne pepper
In a wok or steep sided frying pan, dry fry the mustard seeds over a medium high heat until they begin to pop.
Add the fennel seeds and the butter. Throw in the onions and cook them for a couple of minutes until they begin to brown. Add the ginger and garlic and fry for a further 30seconds Add the chicken with its yoghurt the cardamom seeds and their broken pods. The chicken should sizzle immediately on entering the pan. Fry hard for 6 minutes or so stirring every now and then until coloured. Stir in the tomato puree and add the water and salt. Follow up with the potatoes and beans then turn down the heat and gently simmer all together for 20 minutes or until the potatoes have cooked and thickened the sauce. Eat with cucumber mixed with a little more yoghurt and some chopped mint.