For the chicken tikka, mix all ingredients well in a bowl, cover and leave to marinade for a couple of hours in the fridge. Bring out half an hour before you're ready to grill these (to bring up to room temp) then thread the chicken onto skewers. Place under a very hot preheated grill and cookfor 10 minutes or so, turning halfway. They should be just cook through, charred and delicious looking. Cover loosely with foil and set aside while you make your korma sauce.
For the sauce, add the ghee to a pan over medium/high heat, then toss in the whole spices. Allow them to swell and and awaken for a few moments, then add the onion paste and 1/2 tsp salt. Stir through the fat and allow it to cook, stirring frequently, for 2-3 minutes, or until the moisture has gone, the fat has risen and it has begun to fry. Add the ginger / garlic paste, cook until the raw smell has disappeared, then throw in your ground spices. Stir to combine and cook for several moments before adding the water. A moment of respite! Bring up to a simmer.
Ready your chicken pieces and remaining ingredients as we move fairly quickly here...Add the cashew cream, rosewater and sugar. Bring to a light simmer, then add the chicken, yoghurt, coriander and the remaining 1/2 tsp salt. Heat the chicken through, say 2 minutes. Remove from the heat, sit for a couple of minutes while you prepare your other pieces, then serve. Legit.