Heat oil in a large pan over medium-high heat. Splutter mustard seeds, fennel seeds and cumin seeds. Saute few curry leaves. Add onions, and sauté, for 2-3 mins, or until onions turn light brown. Stir in minced ginger and garlic. Saute until aromatic. Add ground turmeric, ground coriander, ground cumin, 1 teaspoon ground black pepper and chilly powder. Saute for few seconds, or until the raw smell disappears.

Stir in tomatoes. Add enough salt and water (if needed). Mix well. Simmer until oil separates. Add chicken, mix, and bring to a boil. Reduce heat, and simmer until chicken is half cooked. Add 3tsp ground black pepper, and cook, covered, for 10-15 minutes. When done, sprinkle with garam masala and heat through.

Garnish chicken roast with coriander leaves. Serve hot with rice or roti.