Wash the potatoes cook in a pressure cooker for one whistle. Don't overcook as these are small potatoes and you will end up having a mush if you do. I like to add salt at this point as it leaves the potato salted from inside.
Peel the potatoes and keep aside. If some of the potatoes are largish, you can chop them into two slices.
In a heavy bottom pan or kadai, heat oil. Once the oil is hot, add mustard seeds, methi dana, zeera, hing, fennel seeds and coriander seeds and saute for a minute or two.
Add curry leaves and shallots and saute for 5-6 minutes on medium heat.
Add ginger, green chilli and saute for another minute.
Add the dry spices i.e. coriander powder, turmeric powder, red chilli powder, sambhar powder and salt and fry for 3- 4minutes. Add a little sprinkle of water if the masala seems very dry.
Add the potato and toss them well in the masala. Roast for 5-6 minutes. Serve hot with dal/rasam and rice.