First of all boil sweet potatoes in pressure cooker with enough water for 2 whistles, after some time open the cooker lid, drain all the water and let them cool.
Now remove the skin of potatoes and mash with masher then add all the spices powder and salt along with green chillies, coriander leaves and crushed peanuts.
Now squeeze the lemon juice on it and mix all the things very well, it might be very soft so add Rajgira flour as per required.
Now grease your hands with oil or ghee and give the shape of tikkis, heat few tbsp of ghee in a non stick pan and place tikki and fry it on a medium flame.
Once tikki get golden brown from the bottom side flip it and cook on another side also golden brown, remove it to a plate and serve with green chutney.