Set aside the 4 most beautiful asparagus to decorate the dish. Steam the remaining asparagus for 10 minutes, leaving them very al “dente”. Cool in Freddy in a pan for 30 minutes.
Cut them into small pieces. Season with butter and chopped onion. Add flour and cook for a couple of minutes. Add the vegetable broth, stirring constantly. Blend everything with the hand blender and cook for about ten minutes (calculated from when you have reached the boiling).