Put asparagus in a pan with the stock or broth and onion. (Reserve a few tips for garnish)
Cover, bring to a boil, simmer for 6-8 minutes until tender.
Puree asparagus and liquid in a blender (I used my immersion blender)
Melt butter in a large pan, stir in flour and cook, stirring until straw-colored.
Remove from heat and add asparagus puree. Season to taste. Heat to a boil, stirring, reduce heat and simmer 2 - 3 minutes.
Mix egg yolks and cream together then add a little of the hot soup to the mixture to them. Stir well. When the egg and cream has cooled slightly add to soup, stirring constantly so the eggs don't cook.
Reheat carefully without boiling, adjust seasoning.
Pour in a bowl, add tips for garnish, serve and enjoy!