Ghee roast is not a curry. It is a masala roasted in ghee until it gives up its water and clings to the chicken.
We use Byadgi chillies for colour and a few hotter ones for heat, roast whole coriander, cumin and fenugreek, and grind it all with tamarind and garlic.
The trick is the last five minutes: high heat, constant stirring, and taking it off a moment before you think you should.