Heat the vegetable oil in a medium saucepan over high heat. Add the garlic, ginger, and chilis. Cook, stirring constantly until fragrant, about 15 seconds.
Stir in the soy sauce, chicken broth, vinegar, brown sugar, sesame oil, red pepper flakes. Bring to a boil then reduce heat to medium and cook for 1 minute.
Stir the water and cornstarch together until fully dissolved and pour it into the sauce. Cook, stirring constantly until the sauce thickens.
Make ahead tip
Allow the sauce to cool for 1 hour then transfer to an airtight container and refrigerate for up to 4 days. Reheat the sauce by warming it over low heat.
Video
Notes
Green chilis: Any fresh green chile will work. We used serranos. If you're in a pinch, canned green chiles will also work.Red pepper flakes: You can use crushed red pepper flakes or Gochugaru for this recipe.Makes about 2 cups.