In a pot boil the potatoes until well done. Let them cool and peel and dice. Peel and finely chop the onions.
Heat the clarified butter in a saucepan and fry the mustard seeds until they pop. Add the onions and continue frying on low heat until the onions are soft and golden brown. Add the turmeric powder and red chilli powder and stir, then add in the potatoes, sprinkle salt over and toss gently to mix well together.