In a mixing bowl, combine soy sauce, water, rice vinegar, light brown sugar, minced garlic, minced ginger, crushed red pepper, and cornstarch.
Stir well until cornstarch dilutes.
In low to medium heat, add this mixture to a pan.
Stir continuously, and cook it until the sauce thickens to the desired consistency.
Notes
Adjust the heat level by reducing or skipping the crushed red pepper for a milder version, or by adding Sriracha, Thai chili paste, or Sichuan chili flakes for extra spice.
Use it as a marinade for chicken, seafood, or tofu, as a stir-fry sauce, or as a dipping sauce.
Store in the refrigerator for up to a week or freeze for three months. Reheat on the stovetop or in the microwave, adding a splash of water if it thickens too much.