Peel the potatoes, cut into 3 cm cubes and rinse under cold running water for 2 minutes.
Bring a large pan of salted water to the boil.
Add the potatoes and simmer until just tender.
Drain and spread the potatoes onto a wire rack to cool.
Chill for 30 minutes to dry the surface.
In a bowl, combine the red onion, fresh ginger, green chilli, ground cumin, chaat masala, Kashmiri chilli powder and cracked black pepper.
Add the lemon juice and mix well.
Heat the vegetable oil to 180°C in a deep pan.
Fry the potatoes in batches until golden and crisp.
Drain on kitchen paper and season with sea salt.
Toss the warm potatoes with the onion and spice mixture.
Drizzle over the tamarind sauce.
Finish with the fresh coriander and pomegranate seeds.
Serve immediately.