From The Core of an Onion, which was published in November by Bloomsbury.

James Beard once wrote, “I can easily make a whole meal of onion sandwiches, for to me they are one of the greatest treats I know.” According to legend, Beard built his name on an onion sandwich. Bill Rhode was famous for hors d’oeuvre recipes, one of which was finely sliced onion on a piece of brioche. Most great food writers lifted recipes from others, and so Beard, until then a little-known caterer, got a great deal of attention when he published his onion-­sandwich recipe, which was a slice of onion on a buttery brioche.

Even if this story is apocryphal, it is true that, to Beard, an onion sandwich made a great meal. To the Romans, a slice of onion between two slices of bread was a good breakfast. To the British poor, a cheese-and-onion sandwich was basic sustenance. Ernest Hemingway, who grew up eating onion sandwiches in suburban Chicago, of wild-onion fame, liked onions on bread with peanut butter. In his novel Islands in the Stream, the sandwich is referred to as the “Mount Everest Special” because it is “one of the highest points in the sandwich-maker’s art.”

In Ireland, where egg-and-onion sandwiches are popular, the standard version is an egg-salad sandwich with thinly sliced green onions. Back in the United States, President Calvin Coolidge liked his egg-and-onion sandwich made with egg salad, too. His was reportedly a kind of oniony egg salad sandwich on rye bread, with one chopped sweet onion mixed with three hard-boiled eggs, mayonnaise, a little dry mustard powder, salt, and pepper.

In other cases, an onion sandwich is the simplest of concoctions. The writer Joseph Mitchell said of the proprietor of McSorley’s Old Ale House, the venerable Irish saloon in New York City, “He liked to fit a whole onion into the hollowed-out heel of a loaf of French bread and eat it as if it were an apple.” You have to choose from among the great ideas of others.