Soak the sabudana for 4-5 hours or over night. Drain the excess water out and set aside. In a kadhai or pan, heat the oil and add cumin seeds. Let it splutter then add chopped ginger and green chillies. Now add cubed potatoes and let it cook covered for few minutes so the potatoes are almost cooked.
While the potatoes are cooking roast the peanuts if you don't have roasted ones handy. Uncover the pan and add the sabudana, peanuts along with salt, red chili powder and cumin powder. Mix everything well and cover again for a few minutes.
Check to see if the potatoes are done. Check the spices at this time and add if needed as per your taste. Sprinkle some chopped cilantro and give it a stir.
Drizzle some lime/lemon juice. Serve hot with plain yogurt or a mint chutney.