Cut the hard skin off of about 1 inch of a piece of ginger root then use a microplane to grate it into very fine pieces. Peel 3 cloves of garlic and chop it fine or use a garlic press to mince it.
Combine all stir-fry sauce ingredients (Water, soy sauce, brown sugar, cornstarch, black pepper, red pepper flakes, grated ginger, and minced garlic) in a bowl (or large measuring cup), and stir well.
Pour the sauce over your choice of vegetables, tofu, or faux vegan meats at the end of cooking. Cook with the stir-fry sauce for an additional 2-3 minutes until it becomes thick, translucent, and shiny. (This ensures that the cornstarch has been fully activated.)
Notes
You can add 1- 2 tablespoons of sesame oil to the stir-fry sauce for more flavor if you wish or simply stir-fry the veggies in sesame oil.
If you choose to add sesame oil to the stir-fry sauce do so after the cornstarch has dissolved or it will stick to the oil and get clumpy.
Be sure to cook the sauce until it starts to bubble and gets thick, translucent, and glossy.