Sauté the onions in the butter until translucent. Put in sorrel and salt. Cover heat in skillet with the onions until wilted. Sprinkle in flour stir and heat for 5 minuets. Using part of warmed chicken stock puree the contents of the skillet in a blender and return puree to remainder of warmed stock.

Can now set aside and complete at your convenience.

Combine egg yolk and cream in the blender and while the blender is running slowly pour about 2 to 3 cups of warm soup. Do not at any time boil this soup or you will end up with cooked [coagulated] egg which will coarsen the texture. Return the egg soup mixture in the blender to the rest of the soup.

I sometimes add a little curry or cayenne. The French add the butter just before serving.