Blend the onion, tomato, ginger, garlic, dried red chilli into a smooth paste. Add 1-2 tbsp of water if too dry to make a paste.
In a pan add mustard oil followed by cumin seeds. Let them splutter for 2 minutes and add the paste made earlier. Cook it on a medium to high flame for 10 mins.
Add the spices - turmeric powder, chilli powder, coriander powder and mix well. Add the chicken and coat it well with the sauce in the pan. Cook it for 10 mins.
At this stage add water and let them simmer under a lid for 15-20 mins. Stir occasionally. After 20 mins, you will see oil separated at the edges of the pan.
Add garam masala, green chilli and coriander and mix well. Serve this warm with steamed basmati rice. It tastes pure heaven.