In some parts of India it is common to combine a sweet and sour taste, particularly in lentil curries such as this one. Plan in advance when you want to make this dish as the dal has to be Soaked before you cook it.
Soak the lentils in cold water for 2 hours. Rinse the kokum, remove any stones and put the kokum in a bowl with cold water for a few minutes to soften. Drain the lentils and put them in a heavy-based saucepan with 1litre (4