For the soup
For the crispy sage
1. Melt the butter in a large saucepan. When it sizzles, add the olive oil and heat for 30 seconds before dropping in the onions and celery with a pinch of salt. Cook, stirring often for 10 minutes, until softened, then add the squash, potato, garlic, rosemary, and chilli. Cook for 3-4 minutes, stirring occasionally.
2. Pour in the cider and vegetable stock. Bring to a simmer, then season with salt and pepper. Continue to simmer gently for 20 – 24 minutes, until the vegetables are easily crushed when pressed with a wooden spoon against the side of the pan.
3. While the soup is cooking, melt the remaining butter in a frying pan and when it sizzles, scatter over the sage leaves. Use a slotted spatula to move the leaves around until the sizzle dies down. Once the leaves are all curled and crisp on the surface. Pour the leaves and butter through a sieve suspended over a bowl.
4. Scatter the cheese into the soup, then use a stick blender to blitz until totally smooth. If needed, re-heat the soup, then ladle into warm bowls. Top with a few crispy sage leaves and a spoonful of the sage butter from the bowl.
5. Any remaining soup can be stored in an airtight container in the fridge for up to 5days, or frozen for up to 6 months. If frozen, thaw completely before re-heating.