Fill and boil the kettle. Trim the ends from the squash and cut it in half. Scoop out the seeds (compost them or roast them in the oven with some spices for a toasty snack).Chop the squash into small pieces (no need to peel unless you prefer to).
Warm a medium pan on the heat and add 1 tsp oil. Add 1 tbsp Thai red curry paste and fry, stirring, for 1 min. Tip in the squash and stir to coat it in the paste. Pour in the coconut milk and 500ml hot water from the kettle. Bring up to a bubble and simmer for 12-15 mins with the lid on.
While the soup simmers, break 1 bundle of noodles in half and pop them in a large bowl. Fill and boil your kettle again. Pour over enough hot water from the kettle to completely cover the noodles. Set them aside to soak for 6-8 mins. After 6 mins, check to see if they’re ready – if you bite into a noodle it should be tender with no chalkiness. If it’s still a bit chalky, soak for a few mins more, then check again. Drain, rinse with cold water and set aside.
Trim the ends off the spring onions and thinly slice the white and green parts. Roughly chop the coriander leaves and stalks. Finely grate the zest from the lime and quarter it.
When the soup has simmered for 12-15 mins, the squash should be tender. Cook a little longer if it’s still firm. Add the noodles, spring onions and half the coriander to the pan. Simmer for 1 min. Stir in 1 tbsp vegan fischy sauce and squeeze in the juice from half the lime. Taste and add a pinch of salt if you think it needs it.
Ladle the soup into warm bowls and top with the remaining coriander. Serve with the remaining wedges of lime for squeezing.