Shell fresh thuvarai from the pods, measure ½ cup and keep aside.
Bring a cup of water to a boil. Sprinkle 1 pinch salt and add 1/2 cup thuvarai and cook for 5 mins till soft. Switch off and close with a lid and let it be for another 5 mins.
Drain in a colander and keep aside. Meanwhile pressure cook potatoes in enough water for 2 whistles. Peel the skin, cube or crumble them unevenly and keep aside.
In a mixer take grated coconut, shallots, garlic pods, cumin seeds, fennel seeds, dry red chilies and grind to a coarse paste without using water.
Heat pan with oil. Add mustard seeds and let it splutter. Add curry leaves, asafetida and roast for few seconds.
Add cooked thuvarai, cubed potato pieces and mix.
Add ground paste, turmeric powder, salt and mix well. Sprinkle 3-4 tbsp water, mix and close with a lid.
Cook for 5-7 mins over low flame till the mixture is completely dry.
Potato Thuvarai Curry is ready to be served as a side dish with hot rice.