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.