In a medium bowl, whisk together cornstarch and water. Add chicken broth, honey, soy sauce, sesame oil, and red pepper flakes (if using).
Whisk to combine. Use immediately in your favorite stir fry recipe, using a couple tablespoons or more, and simmer until the sauce is thickened.
Notes
Chicken broth: Chicken broth adds the best flavor to this stir fry sauce. Substitute vegetable broth or water to make the stir fry vegetarian.
Yield: This recipes makes about 1 cup of stir fry sauce. It's enough to cook one pound of protein plus veggies (about 4 servings of stir fry with 1/4 cup sauce per serving).
Storage: Store leftover stir fry sauce in an airtight container in the refrigerator up to 4 days.