Peel and finely chop the onion. Peel the parsnips and trim off the very ends. Finely chop them.
Warm a pan for 1 min, then add ½ tbsp oil and the veg. Season with salt and pepper (use white pepper if you have it). Cover the veg with a piece of greaseproof paper. Pop on the lid.
Sweat the veg over a very low heat for 15-20 mins till they’re soft but not browned – stir once or twice to check. While the veg sweat, peel and grate the garlic and ginger.
Lift off the greaseproof paper. Stir in the garlic and ginger. Pour in the coconut milk and add 350ml boiling water.
Stir to mix. Ladle the soup into a blender and blitz till smooth. No blender? Use a hand-held blender in the pan.
Pour the soup back into the pan and warm through for 2-3 mins. Taste and add a little more salt and pepper if you think it needs it. Ladle into warm bowls and serve.