Pre-heat the oven to 430°F (220°C/200°C Fan forced).
Cut the skin off the pumpkin and roughly chop it into smallish chunks. Put the pices into a bowl, drizzle with olive oil and give them a good toss to coat the chunks.
Put the sweet potato whole onto the edges of a large baking tray. Spread the pumpkin chunks out between the sweet potato.
Bake for 45 minutes or until the pumpkin in starting to caramelize around the edges and the sweet potato is soft when you stick a sharp knife into it.
All to cool, then carefully peel the skin off the sweet potato. It should come off quickly and easily but be careful not to burn your fingers.
Peel and dice the onion. Drain the tin of chickpeas. Heat up a drizzle of olive oil in a stock pot. Cook the onions in the pot until lightly caramelized. Add the nutmeg, cumin and cayenne pepper and stir for several seconds until fragrant.
Add the vegetable stock sweet potato, pumpkin and chickpeas. Lightly mash the soup.
Use an immersion blender to blitz the soup until smooth, taking extreme care not to splash yourself.
Cover with a lid and simmer for a further ten minutes or so, stirring frequently to prevent it from catching.