Wash sabudana (tapioca) changing the water 2-3 time and soak with one cup of water, soak 8 hours or more. Sabudana will become all most four time in volume and will be soft.
Heat the oil in a frying pan on medium heat. Test the heat by adding one cumin seed to the oil; if seed cracks right away oil is ready. Add cumin seeds and mustard seeds after seeds crack add turmeric, lower the heat to low. Add sabudana, and salt. Keep stir frying until sabudana becomes translucence, looks like pearls. This should take about another 4-5 minutes. Stir gently and making sure tapioca doesn’t get sticky and stuck to each other. Turn off the heat, and drizzle 3-4 drops of lemon juice and stir.
Transfer sabudana to a wide bowl stir for few minutes with fork making sure sabudana pearls are separated and not sticky. Serve the sabudana at room temperature.
Add 1/2 teaspoon of salt and green chilies to cubed potatoes, mix it well and set aside.
Assembling the Sabudana Bhel, in a serving platter spread the cooked sabudana, sprinkle the roasted peanuts, over peanuts sprinkle the potatoes, then aloo lacha, some more peanuts and drizzle the chutney.