1. Soak the lentils and peas overnight and then rinse several times in cold water.
2. Fill a large pan with 1.5 litres of water and add the turmeric, salt, ginger (in one piece) and lentils/peas. Bring to the boil and cook until the mixture reaches the desire consistency (like a thick soup). Stir ocassionally and add more water if necessary to prevent sticking. Remove from the heat and pick out the piece of ginger.
3. In a small saucepan, melt the butter and fry the cumin seed, garlic and chilli powder for 1 minute. Pour this spiced butter over the daal (don't stir it in), cover and leave to infuse for 5 minutes. Serve with a scattering of coriander leaves.
Serve as a side dish with naan bread or as main course with rice.