Wash the chicken and pat it dry. The chicken should be cut into medium size or what we know as curry cut.
Make a paste of the medium sized onion and marinate the chicken with the ingredients mentioned for at least an hour.
While the chicken is marinating, peel the potato skins, wash them and cut them into medium sized cubes. Finely slice one large onion.
In a wok or a frying pan, heat 2 tbsp of mustard oil. Add green cardamom, cloves, cinnamon and a couple of green chilies. As they start to splutter, add the sliced onions.
Fry the onions over medium heat till they have become golden and then add the marinated chicken pieces. Over high heat, stir the chicken for a couple of minutes. Take half a cup of water in the bowl where the chicken was marinated and pour in that water to the frying pan too.
Add the potatoes and continue frying.
Then reduce the temperature and cover and cook for the next ten minutes. After that remove the cover and you will notice that the chicken has released water. At this point, again increase the temperature and stir and cook the chicken.
Twenty minutes into the cook time, add the cashew paste and the poppy seed paste. Incorporate them thoroughly into the chicken. Add ½ a cup of water if required. Cover and cook for another ten minutes.
Finally add some dry roasted poppy seed to give the grainy texture and a tsp of sugar. Check the salt and add more if required.
Add 2 split green chilies. Add more if you like the extra heat. The chicken and the potatoes should be cooked by now.
Serve posto murgi with steamed rice or luchi or parantha, whatever you prefer.