Heat the oil in a large pan over a medium heat. Add the onion and cook for 5 minutes until soft but not browned.
Stir in the curry powder and cook for 1 minute until fragrant. This blooms the spice and gives the soup much better flavour.
Add the parsnips and potato. Stir to coat everything in the spiced oil.
Pour in the stock, add the salt and pepper, and bring to the boil. Turn down to a simmer.
Cook for 20 minutes until the parsnip is completely soft when pressed with a spoon.
Blend the soup until completely smooth, either with a hand blender in the pan or in a food processor. Take care with hot liquid.
Taste and adjust the seasoning, then serve with bread.