1. Rinse split peas and lentils in as many changes of water it takes for the water to cease being cloudy.
2. Place lentils, split peas and water in a large stock put or Le Creuset Marmite and bring to the boil. Reduce heat to a simmer and add carrot and half the ginger.
3. Cover loosely and simmer for 30 mins. In the meantime, heat butter or ghee in a small fry pan over a medium heat. Add half the sliced spring onions, the remaining ginger and the raisins. Saute 2 mins. Add tomato puree and sauté another minute. Add curry powder, sauté 1 minute then add this mixture to the lentil mixture (at the end of its 30 mins). Add coconut milk and salt and cook over a low heat for another 20 mins. (Add more water if the soup gets too thick). Serve topped with chopped coriander.