Roughly chop the leek and parsnips. Melt the butter in a large saucepan and add the vegetables – cook for 5 minutes, stirring often, then add all but one of the chestnuts.

Cook for a further 5 minutes, then add the white wine. Allow this to reduce by half, before pouring in the vegetable stock. Season with salt and pepper, bring to the boil then cover and simmer for 10-12 minutes, until the parsnip is soft.

Whizz the soup up with a hand blender. If it’s too thick for your liking, add a little more vegetable stock or water until it reaches a consistency you like.

Serve with grilled gruyere on toast. Grate the remaining chestnut over each bowl of soup before serving.