Step 1: Mix the Sauce Base

1. In a small bowl, whisk together light soy sauce, oyster sauce, rice vinegar, and sesame oil (if using). This will be the base of your stir fry sauce.

Step 2: Add Sweetness

1. Stir in the brown sugar and whisk until it is completely dissolved and well combined with the other ingredients.

Step 3: Make the Cornstarch Slurry

1. In a separate bowl, combine the cornstarch and water. Stir to create a smooth slurry, which will thicken the sauce later.

Step 4: Heat the Sauce

1. In a medium-sized saucepan, heat the prepared sauce mixture over medium heat.
2. Add the minced garlic and grated ginger, and sauté for 1-2 minutes until they become fragrant and lightly golden.

Step 5: Thicken the Sauce

1. Slowly pour the cornstarch slurry into the saucepan while whisking continuously to prevent any lumps from forming.
2. Bring the sauce to a simmer and cook for 2-3 minutes, allowing it to thicken to your desired consistency. The sauce should coat the back of a spoon when ready.

Step 6: Ready to Use

1. Once thickened, remove the sauce from the heat. It’s now ready to be tossed with your favorite stir fry vegetables, meat, seafood, or noodles.
2. Alternatively, let the sauce cool and transfer it to an airtight container to store in the refrigerator for up to 1 week.