For the Badische Schneckencremesuppe, first clean or drain the snails.
Melt the butter in a soup pot, add the flour and stir-fry over low to medium heat until light yellow. Increase temperature, gradually pour in vegetable soup while stirring and simmer for a few minutes.
Add white wine and season with nutmeg, lemon juice and salt.
Mix sour cream with egg yolk. Add three to four tablespoons of the soup to the egg yolk and cream mixture. Remove the boiling soup from the heat and whisk the egg yolk-cream mixture into the soup.
Cut the snails into thin slices, add them to the soup and warm them up, but do not let them boil. Serve Baden snail cream soup garnished with parsley.
Baden snail cream soup can also be refined with other herbs.