Roughly chop the red onion, and mince the garlic and ginger together. Saute in a soup pot with a little oil for 3-4 minutes until the onion softens.
Peel and chop the sweet potato into 1 inch cubes, and add to the pan with the onions and toss to coat. Add the red curry paste, stirring so everything is coated and cook for a couple of minutes.
Add the vegetable stock, coconut milk and peanut butter and stir. Cover with a lid and cook for 20 minutes until the sweet potato is completely cooked.
Either use a stick blender to blend the soup, or transfer to a blender and blend until smooth. Finally stir in the lime juice.
Top with an extra swirl of coconut milk, chopped coriander, fresh chillies and chopped salted peanuts.
