Fill your kettle and boil it. Peel and roughly chop the onion. Place a large pan on a medium heat, drizzle in 1 tbsp olive oil and add the onion. Fry gently for 10 mins, stirring often, till soft and glossy.
Meanwhile, peel and grate the ginger and garlic. Finely slice the chilli, flicking out the seeds for less heat. Peel the sweet potatoes and carrots, and chop them into 2-3cm chunks.
When the onion is glossy, add the ginger, garlic, 3/4 of the chilli (keep the rest for garnishing) and 2 tsp ground coriander. Cook for 2 mins, stirring. Stir in the sweet potato and carrot.
Pour in 700ml hot water from the kettle. Crumble in the coconut cream and add a pinch of salt. Stir, then pop on a lid and simmer for 15 mins till the potatoes are tender when pierced with a knife.
While the soup simmers, warm a small, dry frying pan on a medium heat. Tip in the peanuts and toast for 2-3 mins, shaking the pan, till golden. Tip onto a board and cool for a few mins, then roughly chop the peanuts. Pare a few strips of zest off the lime, then cut it into wedges.
Blend the soup till smooth using a hand-held blender in the pan, or whizz in batches in a blender. Add small amounts of hot water to reach your preferred consistency.
Taste the soup and add salt or pepper if you think it needs it. Ladle the soup into warm bowls. Serve topped with the toasted peanuts, remaining chilli, lime zest and with the lime wedges on the side.