Prepare the nettles: Handle the nettles with rubber gloves or use tongs. Wash the nettles in cold water and remove tough stems. Chop roughly if leaves are large.
In a large pan, heat the butter (or olive oil) over medium heat. Add the onion, carrot, and garlic, sautéing until softened (about 5 minutes).
Add potato and pour in stock. Bring to a gentle boil, then simmer for 10 minutes until potatoes are tender.
Stir in vermicelli pasta and cook for 3–5 minutes until nearly done.
Add nettles and simmer for 2–3 more minutes, until they are wilted but still vibrant green. Don’t overcook the nettles—they should stay bright green and visible.
Season with salt, pepper, and thyme.
Stir in lemon juice for freshness.
Serve hot, garnished with Parmesan plus crusty bread on the side.