2) Cut the squash into medium sized cubes, about 2cm across, then place on a baking tray drizzled with olive oil. Roast until soft (this should take 20 minutes). Don't let the edges catch, if they start browning remove from the oven.
3) While the squash cooks, fry the onion, garlic (and fresh chilli if using) in the butter and olive oil until soft. Do this on a low heat for about the same amount of time you roast the squash for.
4) Chop and dice the sweet potato while the squash and onions are cooking.
5) Once the onions and garlic have softened add the squash, sweet potato, stock and crème fraîche into the pan. Season with salt and pepper.
6) Cook until the squash and sweet potato become soft and begin to break down, and then blend until smooth.
7) Pop into a bowl and enjoy!
I used a nutribullet to blend my soup, but this will work with any sort of blender, including a stick blender.