Meanwhile, whisk gochujang, soy sauce, maple syrup, mirin, and 1 cup water in a medium bowl. Pour sauce into a skillet large enough to hold all of the cauliflower florets (a 12″ skillet should do it) and bring to a simmer over medium heat, whisking occasionally. Cook, whisking, until sauce is thick enough to coat a spoon, 8–10 minutes. Stir in vinegar and remove pan from heat.