Preheat the oven to 220˚C.
While you prepare the pumpkin, scrape out the seeds, clean them in a colander with cold water and then dry the in a tea towel. Pop the seeds in a roasting tray tossed with a little melted butter and roast in the oven until toasted. Remove and set aside.
Tumble the pumpkin into a roasting tin with the thyme and toss in a little oil. Season with sea salt and ground black pepper and pop in the oven to roast for 45 minutes or until the edges are slightly charred and tender when pierced with a fork.
In a large pot, heat a drop of oil and fry the onions until they are soft. Stir through the chilli flakes and fry for a further minute.
Discard the thyme and add the roast pumpkin to the pot, along with the coconut milk and vegetable stock. Bring to the boil and simmer for 5 minutes.
Using a hand blender, whizz the soup until you have a velvety smooth consistency. You may need to add more stock or boiling water to get the right consistency. Add sea salt and ground black pepper and check the seasoning.
Serve the soup in warm bowls with a sprinkle of chilli flakes and toasted pumpkin seeds.