Separate out 200 ml of the fresh cream and stir in the 1 tsp of the garam masala, and mix the two inches Melt half the butter in the microwave and mix into this. This is the marinade for the chicken that will go into the gravy.
Cut the chicken into bite sized pieces and soak them in the marinade. Put this in the fridge and let it sit for half an hour.
After half an hour, get the marinaded chicken out and put in an oven that has been preheated to 180 degree celsius, and let the chicken grill with the fan on for 15-18 minutes (if you've got that in your oven, if not, just do it without the fan, but keep checking the chicken to ensure it doesn't lose tenderness).
While you wait for the chicken to get marinaded, boil the cashews and chopped up onions in the water till the onions start losing their colour and become soft.
Once the onions and cashews are boiled, put them in a food processor and blitz them into a fine paste.
Put the oil in a vessel, and when it starts to heat up, put the remaining butter into it. As the butter melts, pour the onion and cashew paste into this and keep stirring for about 5 minutes, till the paste starts to turn brown.
In the food processor, blitz the tomatoes into a fine puree such that no solid pieces are left. Add the puree to the onion and cashew paste in the vessel.
Add the kasuri methi, red chilli powder (preferably MDH Deggi Mirch), garam masala, salt and sugar to the tomatoes, and cover while cooking the gravy. Reduce the gravy till the tomatoes are fully cooked and the consistency is thick. Allow it to cool after for 5-10 minutes.
After the gravy has cooled, add the cream (or milk, if you're being health conscious) and on low heat, keep stirring the cream into the gravy till the consistency looks fine.
Pull out the chicken from the oven and put it into the gravy. Ensure all the pieces are covered in gravy, and serve.