A hefty dose of rice vinegar blended with soy sauce and aromatics gave this Filipino dish its characteristic bright flavor and made for a potent marinade. The coconut milk tended to burn under the broiler, so we added it toward the end. If you can’t find bird’s eye chilies (sometimes called Thai chilies), any small chili will do. Stir the coconut milk thoroughly before measuring it. Look for chicken thighs that are uniform in size; if some are smaller than others, begin to check them early and remove them as they come up to temperature.