Fry the fenugreek and powder it. Grind tamarind, salt and red chilli well and keep aside. Add the sliced big onion and small onion and grind again. Add the powdered fenugreek and mix well.
Heat oil in a pan. Season the mustard and curry leaves. Add the ground ingredients and saute well for about 5 to 10 minutes. When cool, store in an air tight bottle.