Preheat the oven to 180°C/350°F/gas 4. Put 2 parsnips aside for later. Peel the onion, roughly chop with the remaining parsnips (keep the skins on) and peel and finely grate the garlic and ginger. Place the parsnips and onions in a large pan over a medium heat with 1 tablespoon of olive oil, then cover and cook for 20 minutes, or until dark golden, stirring occasionally. Add the garlic and ginger, then scatter over the cumin seeds, 1 teaspoon of garam masala and the lentils and cook for a further 5 minutes. Roughly snap in the uncooked pappadams, then add the stock and simmer for 20 minutes, loosening with a splash of water, if needed.
Meanwhile, speed-peel the reserved parsnips into ribbons until you reach the woody core (discard this bit), blanch for 30 seconds in fast-boiling water, then drain and pat dry. Season with sea salt, then spread out in a single layer over a couple of oiled baking trays. Roast for 15 minutes, or until golden and crisp. Season the soup to perfection, ripple through the yoghurt and divide between warm bowls. Pick over the cilantro leaves, sprinkle with a little garam masala, and top with the parsnip crisps. Feel free to drizzle with chilli oil for a warm glow.
You can make this soup as chunky or as smooth as you like, and if you cook it a little drier, it makes a fantastic side dish as part of a bigger curry feast.