Scrape the outer bumps with a knife. Slice the karela thinly, put into a bowl and sprinkle with salt. Let the karela rest for 20-30 minutes then squeeze out as much of the jouice as you can and finally run under a tap to remove all the salt
In a wok or large deep pan heat the mustard oil
Add the onions and fry until translucent - about 5 minutes
Add the panch phoron and ginger paste and fry, stirring, for a few seconds, so they release their fragrance
Add the turmeric, chilli and mustard paste (or kasundi) and cook very gently until the oil separates signalling that the spices are cooked
Add all the vegetables and stir fry for a few minutes until tey are well covered in the oil-spice mix
Add half a cup of water and salt to taste, then coveer and simmer until the vegetables are tender, adding more water as needed.