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Cream of Potato Soup
1 pint hot riced potato 1 teaspoon grated onion 1/2 teaspoon celery salt 1/2 teaspoon salt 1/8 teaspoon pepper 1 pint boiling water 1 pint milk 2 tablespoons Mazola 2 tablespoons Argo or Kingsford's Corn starch Scald the milk, add the water, potato, onion and seasonings and cook for five minutes. Thicken with the Mazola and cornstarch creamed together. Serve with croutons.
A straightforward pureed potato soup thickened with a cornstarch-and-oil paste rather than a flour roux — a hallmark of the corn-products cookbooks. A few points on measures and method.
- A pint of riced potatoThis is a volume measure of cooked potato pushed through a ricer, not raw weight — about 2 cups, which takes roughly 1 lb (2 medium) russets, boiled or baked and riced while hot. Ricing while hot keeps the starch from turning gluey.
- MazolaMazola was and is corn oil. Any neutral oil works; the fat here is oil rather than butter, which is unsurprising in a book issued to promote corn oil.
- Argo or Kingsford's cornstarchBoth were brands of the Corn Products Refining Company, which published this book. Plain cornstarch is the same product; 2 tablespoons is light thickening for the 4 cups of liquid called for here, with the potato contributing body of its own.
- The thickening is the hingeCream the oil and cornstarch to a smooth paste off the heat, then whisk it into the simmering soup in a thin stream. Dumping dry cornstarch into hot liquid gives lumps that will not disperse, and cornstarch needs to reach a full simmer for a minute or two after it goes in or the soup tastes chalky.
- Don't boil it hard afterwardsCornstarch loses body if held at a rolling boil or reheated repeatedly, and the milk will scorch on the bottom of the pan. Bring it just to a simmer, hold briefly, and serve.
- Scalding the milkScalding means heating to about 180F, just until a rim of bubbles forms at the edge — a holdover from unpasteurized milk. With modern milk it is optional, but it does shorten the cooking time and helps the soup come together fast.
- Grated onionA teaspoon of onion grated on a box grater, pulp and juice both. It gives raw onion sharpness rather than sweetness; if you want the sweeter note, soften a tablespoon of minced onion in the oil first and skip the grating.
- YieldRoughly 6 cups as written, serving four to six as a luncheon course. Pass the soup through a sieve or give it a brief blender pass if you want it perfectly smooth.
This comes from one of the promotional cookbooks issued by the Corn Products Refining Company, whose brands — Mazola corn oil, Argo and Kingsford's cornstarch, Karo syrup — are named directly in the recipes. Such books were given away free or sold for a few cents in the 1910s and 1920s, and they promoted thickening with cornstarch and cooking with a bottled vegetable oil in place of butter or lard; bottled corn oil was genuinely new, though cornstarch had been sold under the Kingsford's name since the mid-nineteenth century. Cream of potato soup itself is older and much plainer; what marks this version as commercial is the oil-and-cornstarch paste standing in for a butter-and-flour roux. The croutons point to a light course rather than a filling one.