Melt the butter in a soup pot, and add the leeks. Cook over medium heat until softened. Add the garlic, cook for a few minutes more.

Add the potatoes and the broth, cover, and simmer until the potatoes are almost tender.

Add the nettles and using a spoon to push the leaves under the liquid. Cover and simmer until potatoes are completely soft and nettle leaves are wilted.

Use an immersion blender, or carefully work in batches with a standup blender, puree the soup until smooth.

Add the cream and stir to combine. Warm over low heat if needed to bring back to temperature.

If desired, serve with a spoonful of crème fraîche.