Soak lentils in cold water for 5 minutes.

Chop garlic, ginger and chilli, and combine in a small bowl.

Chop half of the coriander and set aside.

Drain lentils. Place in a heavy-based saucepan with 3 cups water, the contents of the garlic bowl, a pinch of salt and the turmeric. Bring to the boil, reduce heat and cook for 20-30 minutes, stirring frequently to prevent sticking.

When lentils are completely soft and collapsed remove pot from the heat. Cool a few minutes then stir in the coriander.

Tip dhal into a wide serving bowl.

In a small frying pan heat the mustard seeds with the butter, stirring. When the seeds start to pop, quickly pour over the surface of the dhal. Garnish with the rest of the coriander. (The dhal thickens as it cools.)