Finely chop the onion and garlic and get them started in a glug of olive oil in a heavy-bottomed large pot. Add about ½ teaspoon each of: turmeric & ginger (or about ½ inch grated of fresh) and about a tablespoon of curry powder. Later you can taste and adjust the seasoning. Allow the aromatics to cook over a low/medium heat for about 5 minutes while you cube the sweet potatoes and celeriac.
Roughly cubes the sweet potatoes and celeriac and add to the pot, stirring well to combine the spices, aromatic, and heroes of the soup
Add stock, pouring it until it just covers all the veggies. Bring up to a boil and then reduce the heat to a low/medium so there are small bubbles. Allow everything to cook like this until the sweet potatoes and celeriac are fork tender.
Allow to cool slightly and then blend (with immersion blender if you have, or in 2-3 shifts in a traditional blender.)
Serve with a dollop of yogurt (optional) and chopped cilantro (optional).
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