Marinade your chicken in all the spices and yoghurt listed above for a minimum of 1hr, but ideally overnight.
Sauté your tomatoes, onions, cashews and ginger in oil on med-high heat for 5-6 minutes.
Remove from the heat and allow to cool, once cooled purée in a blender with 4 tbsps of water, until smooth.
Fry your marinated chicken in the butter for 5 minutes or until all the water it releases evaporates.
Add in salt and tomato purée and cook that down for a further 3 minutes.
Strain your tomato and onion mixture into the pan using a sieve and stir well.
Add in your fenugreek leaves and cook for a further 2 minutes on med-low heat.
Turn the gas off and stir in your double cream.
Serve immediately and garnish with chopped coriander and some more cream!