A traditional preparation which is a hot favourite among the Maharashtrians. The field beans are cooked with kokum which imports a subtle hint of sour flavours that are distinctly different from using tamarind or lemon. Kokum is the dried peel of the fruit which is grown along coast. Kokum is available at most grocers.
Soak the kokums in 2 tablespoons of water and leave aside for 10 to 15 minutes. Purée the soaked kokums in a blender to get a smooth paste. Strain and keep aside.
Heat the oil in a non-stick pan and add the cumin seeds. When they crackle, add the asafoetida, curry leaves and ginger and sauté for a few seconds.
Add the onions and sauté till they turn translucent.
Add the vaal and 1 cup of water. Cover and cook for 15 minutes.
Add the turmeric powder, kokum paste, jaggery, chilli powder, coriander and salt and cook for another 5 minutes.