The walleye sandwich is a Great Lakes fish sandwich whose defining quality is the fish, not the build around it. Walleye is a lean, mild, firm-flaked freshwater fillet with almost no oil and a clean, sweet flavor, and that leanness sets every other decision. It cannot survive a long, heavy fry the way an oily ocean fish can, so the coating has to be thin and the cook fast, which is why the sandwich is engineered to defend a delicate fillet rather than to dress a robust one. The bun and the sauce are deliberately quiet so the lake fish stays the headline.
The craft is in the breading and the timing. A walleye fillet is given a light dredge or a thin beer batter and fried hot and brief, just long enough to set a crisp shell before the lean flesh dries out, because an overcooked walleye goes to cotton inside its own coating. The fillet is left close to its natural size rather than pressed into a uniform patty, so the sandwich has the irregular edges and the flake of a fish someone actually caught. A soft bun is chosen so it does not compete with a tender fillet, and tartar or a lemon-forward sauce supplies the acid and fat the lean fish lacks. A pickle or shredded lettuce adds the cold crunch a fried fillet has none of, and the trip from fryer to hand is kept short so the crust is still crisp on the first bite.
The variations follow the lake and the season. The Friday fish fry version serves it as a sandwich on the same plate as the basket; the perch and lake trout builds run the identical light fry on a different Great Lakes catch; the shore-lunch style cooks the fillet pan-fried in butter rather than deep-fried for a softer, less brittle shell. Each keeps the lean-freshwater-fish logic and changes one element around it, and each deserves its own article rather than being crowded in here.