Heat the oil in a saucepan, fry the cumin seed for half a minute. Add the finely chopped onion, ginger, chilli and garlic and fry until the onions turn translucent. Then add the dry spices, and fry for another minute.
Add the lentils, fry for 20 seconds, add the water and bring to a boil.
Simmer for one hour or until the lentils are tender.
Add the salt and a knob of butter and cook for another 5 minutes.
If you like a smooth consistency, you can blend the mixture with a blender.