Add salt to grated potatoes and mix. Knead till smooth. Divide into eight equal portions. Keep aside. Wash moong dal. Soak for half an hour and drain. Heat two cups of water and boil moong dal with salt and turmeric powder till just cooked (al dente). Drain. Heat one tablespoon of oil, add asafoetida, ginger, green chillies and parboiled moong dal and a little salt. Stir-fry for two to three minutes.
Add lemon juice and spread on a plate to cool. Add coriander leaves to moong dal and mix. Divide into eight portions. Take a portion of mashed potatoes in dampened palms, make a dent in the center, put some stuffing and close in the edges to enclose the stuffing.
Press gently and roll the edges on the tabletop to smoothen the sides. Heat a little oil on a tawa and shallow fry tikkis on low heat till they turn crisp. Whisk yogurt and add salt, rock salt, roasted cumin powder and red chilli powder.
To serve, place two tikkis on a serving plate, pour some yogurt, green coriander chutney and sweet tamarind chutney over them. Similarly make other servings.