There is a lovely and informative article (and recipe), as well as a fount of Jane Austen knowledge, at a site called Austenonly: The Interesting History of White Soup.
In Pride and Prejudice, it is mentioned by by Mr. Bingley.
Netherfield Ball White Soup
- 2 1/2 pints veal or light beef stock
- 2 ounces blanched almonds
- 8 ounces white bread, weighed without crusts – approximately the inside of one French country bread from the Harris Teeter bakery 😉
- salt & pepper
- pinch cayenne
- 1 egg yolk
- 1/2 cup sour cream
- 1/2 cup heavy cream
- to serve: lemon wedges, toasted almonds, chopped pistachios, and/or pomegranate seeds
In a medium pot, simmer veal stock, almonds and bread for 20-30 minutes. Blend well in a blender and pass through a sieve back into the pot. Season to taste with salt, pepper, and cayenne, and heat back through.
In a small bowl, lightly beat the egg with a whisk. Ladle hot soup into the bowl a little at a time, whisking constantly, to temper the egg. Pour into pot, stir well, and gently heat for about 10 minutes. Stir in sour cream, and heavy cream, and gently heat through (do not boil).
Serve with lemon wedges and garnishes