The chicken fried steak sandwich is the rare sandwich whose name lies about its main ingredient: there is no chicken in it. A tough, cheap cut of beef, usually cube steak that has already been run through a mechanical tenderizer, is dredged and fried in the manner of fried chicken, which is where the name comes from and where the whole idea begins. The point of the technique is not flavor on its own but rescue. A cut this lean and this worked would be inedible cooked any other way, and a hard seasoned crust plus a pour of gravy is the structure that makes it a meal. Get the breading and the gravy right and the sandwich works; get them wrong and it is a fried shoe between bread.
The craft is borrowed wholesale from the fryer and the lunch counter. The steak is pounded thin and even so it cooks through before the crust burns, dredged in seasoned flour, often double-dipped through buttermilk for a craggy shell, and fried hot. Then comes the decision that defines the sandwich: the gravy. A peppery cream gravy built from the fry drippings is poured over the steak, which means the crust is going to soften, so the bread has to be sturdy enough to take that flood without dissolving. Thick white bread or a plain soft bun is chosen precisely because it is a structural sponge, soaking the gravy and the rendered fat and giving the hands something to hold while the steak does the work. The pickle or raw onion some cooks add is not garnish; it is the sharp, acidic counter a rich, soft, gravy-soaked center needs so it does not read as one heavy note. Timing is the whole game at noon: served fast, the crust still has bite under the gravy; served slow, the sandwich has gone to paste.
The variations stay close to the plate it came off of. The open-face build skips the top slice and serves the steak on bread under a ladle of gravy to be eaten with a knife and fork. The closed sandwich keeps the gravy thin enough to hold one-handed. A fried egg or a slice of melting cheese pushes it toward a breakfast build, and the country fried steak version distinguishes itself with a brown gravy rather than a white cream one. Each of those is a codified reading with its own logic, and each deserves its own article rather than being crowded in here.