Bring a pan of salted water to the boil and cook the potatoes until they are tender. Drain, leave them to cool a bit and then peel. When they have completely cooled, cut them into small blocks.
Mix the yoghurt, cumin and mint in a large serving bowl and season to taste with salt and pepper. Add the potatoes, pepper and shallot and mix through well, taking care not to mash up the potatoes.