Heat the fat. Sweat flour in it. Stir in asparagus stock and milk, bring to the boil and simmer for approx. 5 minutes
Clean and wash the zucchini and slice or slice into fine strips or slices. Season soup with salt, pepper, lemon juice and sugar. Cook the zucchini for 2-3 minutes. Season to taste
Whisk some hot soup with egg yolk and stir into the soup (do not boil any more!). Whip cream until half stiff. Wash and pluck the basil. Serve the soup with cream and basil