Combine: In a small saucepan, combine all of the ingredients except the cornstarch and whisk for a few seconds.
Heat: Place the pan over medium-high heat, covered, and bring to a boil.
Make the slurry: While the sauce comes to a boil, combine the cornstarch and 3-4 tablespoons of water in a small bowl. Whisk with a fork and set aside. This is your thickening agent, so the sauce ends up with the consistency of one that has simmered for hours (but we know better).
Thicken: When the sauce reaches a boil, turn the heat down to medium-low and remove the lid. Add the slurry and whisk constantly for about 10 seconds.
Simmer: Let the sauce simmer for 4-7 minutes, until slightly thickened. To test for doneness, dip a spoon into the sauce and run your finger along the back of the spoon. If it leaves a clean streak, the sauce is ready.
Store: If you're saving it for later, cool it completely before refrigerating.
Use the Sauce
Cook the base: Heat a wok or skillet over medium-high heat. Cook your meat, seafood, or tofu until almost done, adding the vegetables as well.
Add the sauce: Drizzle the sauce into the pan (you won't use all of it) and cook, stirring, until everything is coated and looks glossy and tender. It needs less than a minute since the sauce has already been reduced.
Serve: Serve over rice or the Asian noodles of your choice.