Begin by melting the butter in a large saucepan and then add the shallots and potatoes.
Stir everything together in the buttery juices, then cover the saucepan and cook the shallots and potato very gently for 10 minutes. Next, add the stock and bring to simmering point. Let everything simmer for another 5-10 minutes or until the potato is tender. Now add the spinach leaves, cover with a lid and leave the leaves to collapse in the heat of the pan. Then stir everything together and add a generous grating of fresh nutmeg and season with salt and pepper. Once all the spinach has wilted, take the pan off the heat, leave to cool a little, then blend the soup in batches until smooth (have a bowl ready to put the first batch in).
Then return the soup to the pan and stir in the crème fraîche. When you’re ready to serve the soup, re-heat it gently just up to simmering point and finally, stir in the diced cheese. Ladle the hot soup into warm bowls and, if you like, garnish each one with a scattering of chopped parsley or finely chopped fresh chives.