Catsup Dressing

A creamy, sweet-sour dressing of the sort that filled American salad chapters in the early twentieth century. It comes together in a bowl with a whisk and needs no cooking, but a few of its ingredients are not quite what they were.

• Add the cream last, and slowlyThe order given is the whole technique: the salt, sugar and vinegar are blended with the oil first, the catsup thickens the base, and the cream goes in gradually so it is less likely to curdle against the vinegar. Tipping the cream in all at once, or pouring vinegar straight onto cream, risks a grainy dressing.
• Sweet or sour cream"Sweet cream" means ordinary unsoured heavy or light cream; "sour cream" here means genuinely soured cream, closest today to full-fat cultured sour cream. Sour cream makes a thicker, tangier dressing and is the better choice if you want it to cling to shredded cabbage or a wedge of lettuce.
• Catsup then and nowBottled tomato catsup of this period tended to be thinner and more sharply vinegared and spiced than most modern ketchup, and was not always as sweet. If you use a standard supermarket ketchup, taste as you go and consider cutting the sugar back.
• Olive oilThe recipe does not specify a grade. A grassy, peppery extra-virgin will dominate the cream and catsup; a milder oil keeps the balance better.
• Vinegar strengthNo type is specified. A plain cider or white vinegar is the safest assumption. Wine vinegars work, but avoid anything already sweetened, such as balsamic, since the recipe carries its own sugar.
• Yield and keepingAbout one and three-quarter cups, enough for eight to ten generous salad servings. Refrigerate and use within three or four days; it will thicken and may separate slightly, so whisk before serving.
• What to put it onToo heavy for delicate leaves. It suits iceberg or romaine wedges, cold cooked vegetables, hard-boiled eggs, or shredded cabbage.