Make the mustard paste by grinding mustard seeds, red chilli, garlic, cumin seeds, and coriander seeds into a fine paste.
Put a non-stick pan on the gas and heat oil.
Add punch-phutana to the hot oil and let it crackle.
Add the sliced onions to the pan and stir for a minute or two until they turn brown.
Add the potato pieces to the pan and fry for 5-6 minutes or until they are slightly browned.
Add the Poi Khadi (Malabar Spinach cuttings) to the pan and stir well.
Add turmeric powder and salt to the pan and stir again.
Fry for 5 minutes and then add the mustard paste to the pan.
Pour 3-4 cups of water into the pan and stir everything together.
Boil the mixture properly until the oil comes out from the water and the gravy thickens.
Check the gravy for consistency, it should be moisty and not too runny.
Garnish with chopped coriander leaves and serve hot with rice.