Marination: Crush the fenugreek and fennel seeds into powder.
In a bowl, add chicken and all the marination ingredients. Mix, cover and marinate for at least 2 hours, preferably overnight.
Now add few tbsp oil in a pan and cook the chicken pieces. Set aside.
Gravy: In a wok, add oil, butter, onion, cloves, cinnamon sticks and cardamoms.
Sauté until onion is soft, but not brown.
Add ginger and garlic paste and cook for a minute.
Add tomatoes and cashews and allow to cook until tomatoes are soft and gravy leaves the oil.
Take out and discard cardamoms, cinnamon sticks and cloves
Allow the gravy to cool and blend to a smooth paste in a blender, adding little water if necessary.
Add the gravy back to the wok and add chicken pieces to the gravy.
If the gravy is too thick, add more water, mix and let it simmer on low heat for about 12-15 minutes so that the chicken pieces can absorb the flavors well.
Lastly, add thick cream, mix, cover and cook on low flame for 2-3 minutes.