Given the many changes in the Chinese food world over the last few decades—and particularly the craze for Hunan and Sichuan food unleashed by Nixon's 1972 visit to China—it's surprising to discover that our inclination toward brown sauces probably goes back at least a century. One of our first Chinese cookbooks, the 1917 Chinese Cook Book by Shiu Wong Chan, contains a recipe for "Chinese Gravy" made from a chicken- and pork-flavored stock, cornstarch, and soy sauce, with a bit of salt, sugar, and sesame oil. That was perfect to pour over the ever-popular egg foo young, which a 1936 New York Times article describes as "pancake-like rounds of egg swimming in a rich brown gravy." If that was too difficult, you could simply open a jar of La Choy Brown Gravy Sauce made from "parts of corn, sugar cane, soya beans, wheat and monosodium glutamate" and billed as "essential for coloring or sweetening Chop Suey or Chow Mein." It's no longer made, but the Internet suggests a simple replacement recipe of a teaspoon of La Choy soy sauce to a half cup of corn syrup.

As Americans became (cautiously) more adventurous, they discovered beef with oyster sauce, a Cantonese stir-fry covered with thick gravy. Instead of using a little soy sauce and a lot of stock, this sauce consisted of a half cup stock to a quarter cup of pungent oyster sauce—made from oyster extract, water, cornstarch, MSG, and a few other ingredients—with more cornstarch to thicken and sugar, pepper, and "gourmet powder," i.e. more MSG. To American stomachs, this was the Chinese version of pan-fried steak with gravy. Oyster sauce became a staple of Chinese-American restaurants, even as the Nixon-inspired craze for spicy food swept away dishes like chop suey and chow mein in the '70s. While restaurant owners added bland and greasy versions of kung pao chicken and orange beef to their menus, they saw that their oyster-sauce-based brown sauce retained its power to stimulate jaded American palates. A little legwork in Midtown Manhattan revealed that the current recipe for brown sauce varies little from the Cantonese formula. When I asked about the ingredients at Hop Won on East 45th Street, a cheerful lady behind the counter replied, "Yeah sure, chef's secret!" Then she shouted into the kitchen: "Hey, what's in the brown sauce?" The answer was given by one of the owner's sons: stock, soy sauce, oyster sauce, and a bit of cornstarch.

I now faced a dilemma: I'd unraveled the mystery of brown sauce, but did I have to eat it? The steam table at Hop Won caters to a largely American clientele with brown-tinged dishes like beef and chicken with broccoli, egg foo young, shrimp chow mein, sweet and sour pork, pepper steak, barbecued spare ribs, General Tso's chicken, and other Chinese-American classics. But the restaurant also serves another clientele, which orders from hand-drawn signs taped to the wall that are covered with Chinese characters. If you peek into the kitchen, you'll see that the head chef's wok is flanked by containers holding not only soy sauce, oyster sauce, stock, cornstarch, and MSG, but also hoisin sauce, chili paste, sesame oil, curry powder, white pepper, sugar, salt, and chopped scallions, garlic, and ginger. The choice took only about half a second. I pointed to one of the paper signs.

The chef's metal wok spoon flashed here and there, scooping up ingredients and dropping them in the wok. In went the meat, then the vegetables. He stirred briskly and gave the wok a few shakes, and within a minute or two a delicious South Chinese specialty was steaming on a Styrofoam plate. As another Chinese epigram goes: "For each dish, each style. In 100 dishes, 100 flavors."