Peel and roughly chop the celeriac and parsnips.
Finely chop the onion and garlic. Peel, then finely chop the ginger and turmeric root.
Heat the oil in a pan and sauté the onion for 5 minutes. Add the garlic, ginger, turmeric and cumin seeds, then stir-fry for 2 minutes.
Add the parsnip and celeriac pieces, then the peppercorn and curry powder. Stir for 1 minute.
Pour in the stock, cover and simmer for 15 minutes until tender.
Using a hand-held blender, process the soup until smooth and silky. If it’s too thick, add more stock.
Serve warm.