Preheat your oven to 200°C/Gas 6. Place a roasting dish on the top shelf to heat up.
Quarter your squash. Slice off the woody stem and scoop out the seeds. Discard these. Cut your squash into 2-3 cm hunks. Carve the skin off if you like but it is edible, so leave it on for more texture, if you fancy it.
Gloss the squash with oil. Season well. Tumble into the preheated roasting tray. Cook 25 mins or till the squash is tender and golden.
Get a large pot hot. Thinly slice your onions. Add a good gloss of oil to the pan. Add your onions and a pinch of salt. Let the onions sizzle over medium heat till they get a little crisp. Spoon out of the pot. Set on a clean cloth or a wooden cutting board to help absorb the oil.
Add the coconut milk to the pan. Gently warm. Swirl in the Thai curry paste. Fill the coconut milk tin with water. Bring to a gentle simmer.
Once the squash is roasty toasty and tender, add it to the broth along with the crispy onions. Bowl up. Roughly chop the parsley. Scatter it over the top.