The Korean-American fried chicken sandwich is defined by a crust that is fried twice. The fillet is coated and fried, rested until the steam works out of it, and then fried a second time at higher heat, which drives off the surface moisture and sets a thin, hard, glassy shell rather than the thick craggy crust of a Southern fry. That second fry is the whole identity. It produces a coating engineered to stay crisp under a wet glaze, which is the entire reason the sandwich can be sauced the way it is without going soft.
The sauce is a glaze, not a toss or a paste. Where a Buffalo build coats the fillet in a butter emulsion and Nashville lacquers it in spiced oil, the Korean-American version brushes or tosses the fillet in a thick, syrupy glaze: gochujang with sugar and garlic for the red version, or a soy-garlic glaze cooked down sticky for the other. The glaze clings in a lacquered sheet because the double-fried shell is hard enough to hold it on the surface instead of absorbing it, so the coating crackles audibly under a glossy, sweet-hot, savory coat. The build around it is balanced for that sauce: a soft brioche bun whose sweetness runs with the glaze rather than against it, a tangle of kimchi slaw whose ferment and chile cut the sugar, and pickled daikon, the crisp, sour mu, supplying the bright snap the rich fillet has none of. Each counter is doing structural work, holding a sweet, sticky, fried center in balance.
The variations stay inside the double-fried frame. The soy-garlic and the gochujang glazes are the two settled poles, and many kitchens run a half-and-half. A snowing-cheese version dusts the glazed fillet in powdered parmesan; a scallion-and-sesame build leans savory and drops the slaw. It sits in the same family as the Nashville hot chicken sandwich and the Buffalo chicken sandwich, separate regional answers to carrying an aggressive sauce on a fried fillet, and those relatives deserve their own articles rather than being crowded in here.