Preheat the oven to 200°C.
Cut 12cm off the squash bottom, remove seeds, and roast on a tray for ten minutes.
Peel and chop 150g of the remaining squash.
Heat olive oil in a saucepan and saute chopped garlic for one minute.
Add the 150g of chopped squash to the pan and fry for two minutes.
Pour in 150ml of stock and bring the mixture to a boil.
Simmer for ten minutes until the squash is tender.
Stir in the milk, season with salt and pepper, and let cool slightly.
Blend the mixture in a food processor until smooth and strain through a sieve.
Pour the warm soup into the roasted squash base and garnish with coriander.