Mushroom Soup
1/2 lb. mushrooms 4 cups White Stock III 1/4 cup pearl sago 1 cup boiling water 1 cup heavy cream Yolks 2 eggs Salt and pepper Clean and chop mushrooms, and add to stock. Cook twenty minutes and rub through a sieve. Cook sago in boiling water thirty minutes, add to stock, and as soon as boiling-point is reached, season with salt and pepper; then add cream and yolks of eggs.
A cream-and-egg-thickened mushroom soup of the sort taught in early twentieth-century cookery schools, thickened with sago rather than flour. The whole dish hinges on the last step.
- Never boil after the yolks go inOnce the cream and yolks are stirred into the hot soup, keep it below a simmer or the yolks will curdle into threads. Beat the yolks with a little of the hot soup first, return the mixture to the pan off the heat, and warm it gently until it thickens.
- White Stock IIIThis refers to another recipe in the same book: a mild light stock from veal or fowl, unbrowned and lightly seasoned. Any unsalted light chicken or veal stock works; avoid a dark brown stock, which will muddy both the colour and the mushroom flavour.
- Pearl sagoSago is a starch from the sago palm, sold as small opaque pearls. Small pearl tapioca is the closest common substitute in the same quantity. The recipe cooks it separately in boiling water; doing so as directed keeps the pearls from soaking up the stock and thickening the soup more than intended.
- Sago timingThirty minutes is what the recipe specifies. Modern small tapioca pearls are often tender sooner, perhaps 15 to 20 minutes; cook until no white centre remains, then add with their water.
- SievingThe instruction to rub through a sieve predates the blender. A stick blender or food processor does the work in seconds; pass it through a fine sieve afterwards if you want the smoothness the original intends.
- MushroomsHalf a pound of ordinary cultivated white mushrooms suits this; cremini work as a modern alternative. For more depth, brown half of them in butter before adding rather than lengthening the twenty-minute simmer.
- SeasoningSalt after the sago and before the dairy, as written. The cream flattens salt perception, so taste again at the end and correct off the heat.
- YieldAbout four cups of stock plus cream and sago gives roughly six small first-course servings, or four generous bowls.
Sago and tapioca were common thickeners in Anglo-American cookery before roux-based cream soups took over, and were often recommended for invalid and nursery cooking. A soup finished with cream and egg yolks is the classic liaison of French practice, and its appearance in a domestic-science manual of this kind reflects how far professional technique had reached American household teaching by the early 1900s. Cultivated mushrooms were still relatively costly at the time, grown in cellars and similar underground spaces and sold in small quantities.