Heat oven to 200C/180C fan/gas 6.
Toss the pumpkin or squash in a roasting
tin with half the oil and seasoning, then
roast for 30 mins until golden and tender.
Meanwhile, put the remaining oil in a
pan with the onion, ginger and lemongrass.
Gently cook for 8-10 mins until softened.
Stir in the curry paste for 1 min, followed
by the roasted pumpkin, all but 3 tbsp of
the coconut milk and the stock. Bring to
a simmer, cook for 5 mins, then fish out
the lemongrass. Cool for a few mins, then
whizz until smooth with a hand blender,
or in a large blender in batches. Return
to the pan to heat through, seasoning
with salt, pepper, lime juice and sugar,
if it needs it. Serve drizzled with the
remaining coconut milk and scattered
with chilli, if you like.