- Warm 2 tablespoons of oil in a deep pan. Add the onions, celery, and a pinch of salt. Cook gently for 10 minutes, until starting to soften.
- Add the beetroot, curry paste, garlic, ginger and cumin. Cook for 2 more minutes.
- Meanwhile, smack or press the bulb end of the lemongrass (e.g. with the flat of a knife), until bruised and split but still in one piece. Pull 3 long strips of zest from one of the limes with a peeler.
- Add the lemongrass, lime zest, coconut milk, and stock to the pan. Bring to a simmer and season with salt. Cook gently for 25 -30 minutes, or until the beetroot is completely soft.
- Remove the lemongrass and lime zest from the pan and discard. Add a good squeeze of lime, and blend the soup until completely smooth, adding a dash of hot water if it seems too thick. Taste and tweak with more salt and lime juice to your liking.
- Divide between bowls and garnish with coconut flakes and coriander.
Cooking time for beetroot can vary depending on the season. Summer bunched beetroot will cook a little faster than winter beetroot so be aware that cooking times may vary.