Grind all the ingredients mentioned under 'For the marination' to a fine, smooth paste.
Wash the chicken well and leave it to drain on a colander for about 10 minutes. Then transfer it to a bowl and mix it well with the marination. Keep aside for 15-20 minutes or overnight in the fridge for best results.
When you are ready to cook the chicken, place a wide base pan or wok on a medium heat and add the ghee. When it is hot but not smoking, add the fennel seeds and let them sizzle
Add the curry leaves and when they stop spluttering add the sliced onions and fry them till they turn golden.
Now add the marinated chicken and fry it well on a high heat for 2-3 minutes.
Then turn down the heat to a medium low and cook uncovered till the ghee begins to separate. Add water only if required - the stock from the chicken is enough to cook it. Keep an eye on the chicken and stir every now & then so that it does not get scorched.
When the chicken is almost done, add the slit green chillies and simmer for 2 mins. Add the fried capsicum and the coriander leaves.
Sprinkle the garam masala powder and mix gently. Serve hot with rice or chapathis