For making this recipe well - its best to get most of the prep done before hand. Slice the onions, peel and chop the potatoes, keep the dry poha in a colander ready.
In a wok/pan, heat oil. Add the mustard and cumin seeds, let them splutter. Add the curry leaves, green chillies and the heeng. Add the onions and fry until they start to soften. You don't want them to take much colour.
Add the chopped potatoes, turmeric, salt and mix to coat evenly. Add the hot water and cover and cook until the potatoes are 90% done.
Run cold water through the poha in your colander and let the water run clear, be careful not to over-mix so the poha can retain its shape. Get rid of any excess water.
Add the washed poha to the onion-potato mix along with sugar. Combine gently. Once you add the poha, it quickly absorbs any liquid in the cooking potatoes. Taste for seasoning and add the lemon juice. Mix through. Turn off the heat and let it rest for 15-20 minutes before you eat. This helps the poha to settle down and be separated and fluffy.
Garnish with crushed peanuts and coriander leaves. Serve with some crispy sev.
Notes
Typically, onion is not added if any religious puja (worship) is to be performed, so the recipe can be made with or without the onion. If not using onion, add the potatoes after tempering the spices.