Grind into a paste ginger, garlic and chillies, adding 2 tsp water. In a bowl, rub this paste all over chicken. Add tomato, lemon juice, 1 tsp salt, chilli, cumin and garam masala powders, coriander and mint leaves, and curd. Mix well, cover and keep aside 2 hours or refrigerate overnight. When ready with marinated chicken, pour water (5 cups) in the cooking pot.