Heat the rapeseed oil in a large pan and cook the onion until starting to caramelise. Add the vegetable stock cube, cauliflower and drained butter beans. Stir, then pour in the milk and water. Season and add a grating fresh nutmeg. Cover and simmer for 20 mins. Blend the soup with a hand blender until smooth, adding more liquid if necessary. Add the Dijon mustard, extra mature cheddar and double cream. In another pan, sizzle a handful sage leaves in 50ml oil until crisp. Ladle the soup into bowls. Top with the sage, oil and some chopped toasted hazelnuts.