[1] She is supposed to have used this soup to soothe her chest and found it to be beneficial to her voice before performances.
[1][2] The dish is made from mashed rutabaga or sago,[1] chicken stock thickened with a roux, Gruyère cheese, sage, egg yolks,[1] and heavy cream,[1] and topped with beaten egg whites.
(This topping, unfamiliar to many, is a common tradition in French cuisine de famille, as it uses up the whites left over from using the yolks as a thickener).
The soup is mentioned in Isabella Beeton's Mrs Beeton's Book of Household Management (1861) which draws on Eliza Acton's Modern Cookery for Private Families (1847); Acton based her description on Mary Howitt, translator of Swedish writer Fredrika Bremer.
[3] Leopold Bloom, a character in James Joyce's Ulysses, fantasizes about it while lunching in the Ormond Hotel: "Jenny Lind soup: stock, sage, raw eggs, half-pint of cream.