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Fish Soup, with Potatoes
Have ready the fish broth, made as directed for fish soup. When strained, grate a number of potatoes--four pounds of good mealy ones will thicken two quarts of broth--add these with some well-beaten eggs and a large cup of cream. Flavour with salt and nutmeg. If preferred, milk may be substituted for some of the broth, and the cream may be omitted. Serve with klosse or toasted bread. Time, half an hour. Sufficient for eight persons.
A thickened fish soup of the German school, where grated raw potato does the work of flour. The technique is sound, but two points decide whether it comes out silky or grainy and curdled.
- The hinge: the eggs must not boilBeat the eggs with the cream, then temper them with a ladle or two of the hot broth before stirring the mixture back into the pot. Hold the soup below a simmer from that moment on, around 175F; a boil will scramble the eggs into threads.
- Grate the potatoes at the last minuteRaw grated potato browns within minutes of hitting air. Grate directly into the simmering broth, or into a bowl of cold water and drain hard, or the soup takes on a grey cast.
- Four pounds is a lot of potatoFour pounds grated into two quarts gives a very stiff, almost porridge-like soup by modern taste. Start with half that quantity, cook ten minutes to see how it sets, and add more if you want it spoonable rather than pourable.
- "Mealy" potatoesHigh-starch, floury varieties: russet or King Edward. Waxy potatoes such as new or salad potatoes will not break down and will leave shreds suspended in the broth; all-purpose varieties such as Yukon Gold fall somewhere in between.
- Fish brothThe recipe sends you back to the book's separate fish soup for the base; presumably a stock built on fish trimmings. Bones from any lean white fish work; avoid oily fish such as mackerel or salmon, which turn a broth muddy. Twenty to thirty minutes of simmering is enough, longer makes it bitter.
- KlosseGerman bread or potato dumplings, poached separately and dropped into the bowl at serving. Toasted bread is the alternative the recipe offers, and it needs no explanation.
- NutmegGrate it fresh and use less than you think: a quarter teaspoon across eight servings. Pre-ground nutmeg is flat and, in a pale soup like this, tastes dusty.
- Timing and yieldThe half hour covers cooking the grated potato through and finishing with the liaison, not the making of the broth. Eight servings as written, though at the reduced potato quantity it reads more like six generous bowls.
The combination of grated raw potato as a thickener, a liaison of egg and cream, and Klösse alongside places this squarely in the German and Central European kitchen, and Cassell's has kept the German word rather than translating it. Potato as a soup thickener spread through northern Europe in the nineteenth century as the crop became a staple rather than a curiosity. That it appears among the fish soups may reflect the book's arrangement: Cassell's New Dictionary of Cookery seems to gather variations under a heading, so a reader who had already made the plain fish broth on a previous page is simply sent back to it here. The instruction to swap milk for some of the broth and drop the cream entirely is the kind of frugal alternative these compendia often offered.