Dry roast coriander seeds, fennel seeds, 1 tbsp split black grams, black peppercorns and round red chillies in a small non-stick pan till fragrant. Remove from heat, cool down to room temperature and grind to a fine powder.
Heat 2 tbsps oil in another non-stick pan, add onion and sauté till it turns translucent.
Cut potatoes into big cubes and add to the pan. Add salt, turmeric powder and ½ cup water and mix well. Add 1 tbsp ground powder and mix well. Store the remaining ground powder in an airtight container to use later. Cook for 3-4 minutes.
For tempering, heat remaining oil in the small non-stick pan, add 1 tsp split black gram, mustard seeds, asafoetida and curry leaves and let the seeds splutter. Add red chilli powder and mix well.
Add the tempering to the potatoes and mix well. Cook for a couple of minutes.
Transfer into a serving bowl and serve immediately.