In a medium bowl, whisk together cornstarch and water. Add chicken broth, honey, soy sauce, sesame oil, and red pepper flakes (if using).: The moment you start whisking you'll notice the slurry thicken slightly and become opaque, and you want it smooth and lump free. Use a steady wrist motion so the corn starch dissolves fully into the water , watching for any small specks that indicate under mixing. The goal is a uniform pale mixture, not grainy, because lumps will burst unevenly when heated and create gritty pockets. A common mistake is adding the starch directly to hot liquid, which causes immediate clumping and a lumpy sauce. If that happens, strain the sauce through a fine mesh and whisk vigorously while warming slowly to reincorporate.
Whisk to combine. Use immediately in your favorite stir fry recipe, using a couple tablespoons or more, and simmer until the sauce is thickened.: When you combine these, the aroma shifts immediately, with the honey lending a sweet perfume while the soy sauce offers a deeper savory note. Pour the chicken broth in first so the slurry disperses more easily, then add the honey and soy sauce , stirring until glossy. The toasted sesame oil will float slightly at first, releasing a nutty scent as it warms. If you included the red chili flakes , they'll add a sharp peppery note that you can smell even before heating. Avoid over stirring which can introduce too much air and create a foamy texture when heated; gentle but thorough mixing is best.
Whisk to combine: As you whisk, the mixture should become uniformly colored and slightly viscous, with the oil integrating into the liquid. This step is where the sauce's final sheen begins to form, and you can test a small spoonful to judge balance. If the sauce tastes overly salty, a tiny splash more honey or a little extra chicken broth will smooth it out. A frequent error is under tasting at this stage; doing so means you might reduce a sauce that is already too salty or sweet. Adjust carefully, because simmering concentrates flavors.
Use immediately in your favorite stir fry recipe, using a couple tablespoons or more, and simmer until the sauce is thickened: When you add the sauce to a hot pan, listen for a gentle hissing or sizzling as it meets oil and cooked vegetables or protein. The visual cue to watch for is the sauce going from glossy liquid to a thicker glaze that clings to pieces, usually after a minute or two of simmering. Stir or toss constantly so it coats evenly, and if you see the sauce becoming too thick or sticky, add a tablespoon of chicken broth at a time to loosen it. A common slip is adding too much sauce at once which can cool the pan and prevent proper thickening; instead add in stages so the pan stays hot and the sauce reduces correctly.