Make sure to chop all the veggies approximately the same size.
Steam or microwave the veggies until fork tender. Keep ready.
Heat 3tbsp oil in a large pan. Add the panch phoron and hing; once the seeds start to splutter, add the green chilies and cook for 30 seconds.
Add the steamed veggies, season with salt and sugar (if using) and mix well.
Cook till all of the water from the veggies completely evaporates and the veggies are completely cooked through and dry.
Drizzle mustard seeds, if using, and take it off the heat. Serve with rice or just as is.
Sprinkle with fried vadis on top before serving.