WHEN I FIRST BEGAN to write about food, in the long-ago 1980s, I thought I’d be talking about basics that every home cook should know, like how to make a mayonnaise. (“Should” was what I meant, although I didn’t say so and I try to avoid “should.” Now we’re aware of so many more food cultures that there’s no group of preparations every home cook should know.) Despite my initial thought, mostly I went beyond basics, and somehow I never got around to writing about mayonnaise until now. Maybe it seemed too obvious, but it isn’t quite.