Mix dry stuff first. In a small bowl, whisk together the brown sugar, garlic powder, onion powder, and cornstarch. Keep it separate—you’ll thank me.
Combine wet ingredients. In a small saucepan, stir together soy sauce, hoisin, oyster sauce, and water. Heat over medium flame until warm.
Whisk in dry mix. Slowly add your sugar-spice-cornstarch blend, whisking constantly. You want smooth, lump-free sauce.
Simmer & thicken. Let it bubble gently for 3–5 minutes. Watch it! Too long and it gets gloppy; too short and it’s watery. Find the sweet spot.
Finish with sesame oil. Turn off heat, stir in that last touch of sesame oil. Boom—flavor explosion.
Taste & tweak. Sweet enough? Salty enough? Play with it. Remember, cooking is about taste-testing like a pro (or a glutton, same difference).