Rinse you nettles in water or let then soak in water to remove small insects and pollen. Boil the leaves in slightly salted water for one minute. Lift them in a sieve and rinse with cold water. Press out the excess water.
Chop your onion into small cubes. Fry the onions with the butter until they become soft.
Add the wheat flour in with the onions. Add milk in small batches while stirring at the same time with a whisk. Have the soup on medium heat.
When you have added all your milk. Add in the nettles and the spices.
Use a hand mixer to make a smooth soup. If you don't own one, you can use a blender.
Serve for example with hard-boiled eggs or roasted nuts and seeds.
Notes
If you don´t own a mixer, you can chop the nettles finely after blanching with a knife before adding to the soup.