Heat the oil in a large pan over a moderate heat until hot. Add the mustard seeds, cumin seeds, fenugreek seeds, chillies, peppercorns, bay leaves and cinnamon stick. Let them sizzle for a minute until they begin to pop and jump around the pan.
Add the onion and fry for 2-3 minutes until soft and lightly golden. Add the garlic and fry for a further 1 minute. Add the turmeric and chilli powders and stir briefly before adding the chicken. Stir fry for 4-5 minutes until the chicken is lightly fried and the pan hot again.
Add the lentils and then pour in the coconut milk. Fill the can and pour in two more can-fulls of water (28oz/800ml). Season with salt.Let this come to a simmer and then reduce the heat to low and let it bubble, partially covered with a lid for 15 minutes. Remove the lid and gently simmer, uncovered for 25 minutes. Stir frequently to avoid sticking.
The moong dal will break up completely to create a rich, creamy sauce. The chana dal should be intact but soft.
Garnish with whatever you like - I like a simple garnish of fresh chopped tomato and sometimes a little cilantro. Serve with plenty of fluffy basmati rice or Indian breads.