Oil Dressing
2 yolks (one cooked and one raw). 1 cup oil. Juice 1 lemon. 1/2 teaspoon salt. Pinch white pepper. 1/2 teaspoon mustard. Little onion juice. Beat raw yolk light, add the cooked yolk mashed. Then add oil gradually, little lemon at a time. Season and keep in cool place. One yolk hard-boiled egg will be best. Add whipped cream.
This is mayonnaise built on a half-cooked yolk base, a common turn-of-the-century insurance policy against the sauce breaking. Everything depends on how slowly the oil goes in.
- The hinge: add the oil drop by drop"Gradually" here means a few drops at a time until the emulsion visibly thickens and takes on a pale gloss, only then a thin steady stream. Any hurry at the start will leave you with a slick, curdled mess.
- Why the cooked yolkThe mashed hard-boiled yolk adds emulsifying lecithin without adding liquid, and it makes the sauce far more forgiving for a cook working by hand with a fork or whisk. Push it through a sieve first; lumps of set yolk will not smooth out later.
- Alternating oil and lemonThe lemon juice is not a finishing seasoning but part of the structure. Adding "a little at a time" between additions of oil thins the emulsion just enough to keep accepting more fat, and it should be worked in rather than stirred through at the end.
- MustardIn a recipe of this date and measure this most likely means dry mustard powder rather than prepared mustard from a jar. It helps the emulsion as well as seasoning it.
- Onion juiceA period technique: grate a piece of onion on the fine side of a box grater and press the pulp through a sieve, or scrape a halved onion with a spoon. A quarter-teaspoon of juice is ample; chopped onion will not do, as the texture must stay smooth.
- The oilOlive oil and cottonseed oil were both in common household use at this date. A neutral oil, or olive oil cut half and half with a neutral one, gives a milder result; a strong extra-virgin oil beaten hard can turn bitter.
- The whipped creamThe recipe gives no quantity; fold in unsweetened whipped cream just before serving. It lightens the dressing for fruit salads and delicate greens, but it will not hold, so do not add it to the batch you intend to keep.
- Storage"A cool place" meant a larder or icebox. Refrigerate in a covered jar and use within three or four days; the yolk is essentially raw, and anyone cooking for the very young, the elderly, or the pregnant should use pasteurised eggs.
- YieldAbout a cup and a quarter without the cream, enough to dress salad for eight to ten.
Mary A. Wilson wrote for the Philadelphia Public Ledger and had worked in food conservation during the First World War, which shows in a book full of dressings built from a single lemon and a cup of oil rather than from bottles. The half-cooked-yolk mayonnaise is often said to have been a beginner's safeguard, on the reasoning that a broken emulsion wasted an expensive cup of oil, though how widely it was practised is hard to establish. Mayonnaise itself is traditionally traced to the port of Mahón in Minorca, taken up by French cooks in the eighteenth century, though the story is repeated more often than it is documented. The whipped cream at the end marks this as the softer, sweeter-leaning dressing that American households liked on fruit and moulded salads.