Put the lentils, onion and tomatoes in a pan with the turmeric and 1 tsp salt. Add water to cover by 2cm, then simmer gently for 20 minutes or until the lentils are tender.
Heat the vegetable oil in a separate pan and cook the mushrooms until golden brown all over and they have reabsorbed any liquid in the pan. Add the spices and cook for 2 minutes, then stir in the ginger, garlic and chilli. Cook for a few minutes then tip in the tomato and lentil mix, plus 200ml water. Simmer for 20 minutes, then stir in the coriander and yogurt, and serve with rice and naans.
