Place the lentils in a deep bowl and cover with cold water. Leave to soak for 10–12 hours. Transfer to a colander and rinse under cold running water. Drain and place in a saucepan with half the measured water. Bring to the boil, reduce the heat to low and simmer for 35–40 minutes until tender. Drain and set aside.
Heat the oil in a large saucepan over a medium heat. Add the onion, garlic, ginger, chilli, cumin seeds and ground coriander, and stir-fry for 5–6 minutes until the onion is soft and translucent. Add the turmeric, paprika, kidney beans and lentils, and stir thoroughly.
Add the remaining measured water and bring back to the boil. Reduce the heat to low and simmer gently for 10–15 minutes, stirring often. Remove from the heat and season to taste. Stir in the coriander and sprinkle over a little extra paprika. Serve immediately with the yogurt.