another 5 minutes. Remove the pan from the heat and strain the liquid through a fine sieve into a bowl. Set the vegetable stock and the vegetables aside in separate bowls. Melt 2 tablespoons of butter in the pan over moderate heat. Remove from the heat and stir in the flour. Slowly pour in the hot vegetable stock, beating vigorously with a wire whisk and then beat in the milk. In a small bowl, combine the egg yolk and cream. Whisk in 1 cup of the hot soup, 2 tablespoons at a time. Now reverse the process and slowly whisk the warmed egg yolk and cream mixture back into the soup. Add the reserved vegetables to the soup and bring to a simmer. As soon as it comes almost to a boil, reduce the heat, add the cooked shrimp and simmer uncovered over low heat for 3 to 5 minutes or until the shrimp and vegetables are heated through. Taste and season the soup with white pepper as well as additional salt if necessary. Pour into a soup tureen and sprinkle with finely chopped parsley or dill.