Heat 2 tbsp olive oil in a large sauce pan, then gently cook 2 finely chopped onions for 5 mins, until soft but not coloured.
Add 1kg pumpkin or squash, cut into chunks, to the pan, then carry on cooking for 8-10 mins, stirring occasionally until it starts to soften and turn golden.
Pour 700ml vegetable or chicken stock into the pan and season with salt and pepper. Bring to the boil, then simmer for 10 mins until the squash is very soft.
Pour 150ml double cream into the pan, bring back to the boil, then purée with a hand blender. For an extra-velvety consistency you can pour the soup through a fine sieve.
Add a handful of pumpkin seeds to the pan, then cook for a few mins more until they are toasted.