Ok, so this peaked my interest, so I did some googling. If this soup were to be genuine, references to it should exist. In the 1968 'Report on soups' by the Br

Ok, so this peaked my interest, so I did some googling. If this soup were to be genuine, references to it should exist. In the 1968 'Report on soups' by the British Ministry of Agriculture (https://archive.org/embed/op1268165-1001 https://archive.org/embed/op1268165-1001), there is a reference on page 19 to this exact soup (called 'Windsor soup', 'Brown soup' or 'Eton soup'). It even lists the a basic list of ingredients. So this means this soup indeed exists. Now some further digging. Are there old references to either 'Windsor soup', 'Brown soup' or 'Eton soup' in non-fictional media? The 1892 'The encyclopædia of practical cookery' does not list this soup, although it is quite sparse on soups. The 1844 'A New System of Domestic Cookery' list a large amount of soups, none even vaguely hinting at the same name. However, the 1906 'High-class cookery recipes' (https://archive.org/embed/b21528597 https://archive.org/embed/b21528597) lists a 'Windsor soup' which should have a 'brown colour' as the basis. I think that should qualify as a 'brown roux' basis which at the very least lends some credence to a brown 'Windsor Soup' although I cannot verify the color myself. Anyway, that's the result of about 15 minutes of googling. At the very least, it makes me a bit sceptical of the article.