Wash the buckwheat and toss well. Toast the grains in a dry frying pan. Remove from pan and set aside.
Heat up the oil in the pan and add the mustard seeds, dried chillies and curry leaves. When the mustard seeds start to pop, add the onion, ginger and green chilli.
When the onion turns translucent, return the buckwheat to the pan and stir until the grains are coated with oil. Mix tamarind paste and water. Add 1 cup of liquid to the pan and once absorbed, add some more liquid. Test the consistency of the buckwheat and add more tamarind liquid as necessary until the grains are tender.