For this simple spin on Korean buldak, which translates as “fire chicken,” you will need a large broiler-safe skillet. Gochujang, or Korean fermented chili paste, is a key ingredient. Look for it in the international aisle in supermarkets or in Asian grocery stores. Different brands can vary in spiciness, so you may want to start with the smaller amount, then taste after whisking with the vinegar and soy. If desired, whisk in additional gochujang, keeping in mind that the flavors in the finished dish will be slightly more concentrated. Serve with rice and, if you like, lettuce leaves for wrapping.