Cold Asparagus Soup

• 1 dessertspoonful of butter
• 1 dessertspoonful of plain flour
• 1

Heat the butter in a stewpan, add the flour to make a roux and stir well over a gentle heat for a few minutes. Heat the milk, pour it onto the butter and flour mixture, stirring until smooth, and cook for 15 minutes. Heat the asparagus water and pour it onto the white sauce, stirring well, then add the asparagus heads. Cook for 20 minutes, and strain through a sieve. Mix the egg yolk wit