In a small bowl or jug, combine the sauce ingredients and give them a quick whisk. Set aside.: When you whisk the sauce, the aroma of soy sauce and rice vinegar mingles with sweet honey and brown sugar, creating an inviting scent that hints at the final dish. The texture should be silky, not grainy, so whisk until the cornstarch dissolves and the liquids look homogeneous. Doing this step ahead prevents lumps later, and you will notice the mixture shine slightly when it is well combined. A common mistake is adding the cornstarch dry into a hot pan which causes clumping, so always pre mix. If the sauce smells too sharp, a touch more honey smooths it out, but add sparingly so it does not become overly sweet.
In a skillet over medium heat, heat the oil, and cook the chicken (I like to season it with freshly cracked black pepper – optional) and cook for 5 minutes until golden and cooked through. Remove the chicken from the skillet, and set it aside.: As the vegetable oil warms, it will shimmer and deliver a faint toasted scent, signaling it is ready. When you add the cubed chicken , listen for an immediate sizzle, and watch the edges turn a warm golden brown, which locks in juices and creates flavor. Cook in a single layer to promote even browning, and avoid crowding the pan which can steam the meat and prevent crisping. After about the time it usually takes to hum a short tune, check for an internal change from translucent to opaque. Transfer the chicken to a plate so it rests while you cook the vegetables; this prevents overcooking. A frequent error is flipping too often, which disrupts browning, so let the pieces sit for a solid minute before moving them.
Add more oil to the skillet, and saute the vegetables for 3-4 minutes until just softened. Make sure not to cook them for too long, as they'll be cooked for longer with the sauce.: As you add the additional oil and then the broccoli and diced bell peppers , the pan will sing with a lively sizzle, and the vegetables will release a fresh green aroma. Stir constantly to expose all surfaces to heat, aiming for bright color and a slight yielding when pierced with a fork. The goal is tender crisp, so end this phase before the vegetables are fully soft, because they will finish cooking when the sauce returns to the pan. Overcooking here results in limp, colorless veg, so watch for a glossy sheen and vibrant hues as your cue to stop.
Give the sauce a quick whisk, and add it to the skillet. Cook over low-medium heat for 2-3 minutes until it thickens. If it's thickened too much, add a splash of water to loosen it.: Pouring the pre mixed sauce into the hot pan should produce a gentle bubbling, and you will see the liquid transform from thin to velvety as the cornstarch activates. The aroma builds with intensified sweet and savory notes, and the sauce will begin to cling to the vegetables. Stir gently and watch for a translucent, glossy coat that coats a spoon. If it firms too fast and becomes gluey, add small amounts of water to bring it back to a saucy state. Resist stepping away during this thickening stage, because cornstarch can change texture quickly, and catching it early keeps the mouthfeel pleasant.
Add the chicken back in and stir to make sure that it's well coated in the sauce. Remove from the stove, and garnish with toasted sesame seeds, and serve over cooked jasmine rice.: Reintroducing the resting chicken allows the pieces to warm through and become evenly coated, creating a unified bite where protein and sauce are married. Stirring brings out a glossy sheen and releases a finale of combined aromas. Once everything is heated and evenly sauced, remove the skillet from heat to avoid breaking down the texture of the vegetables and overcooking the chicken . Sprinkle the toasted sesame seeds for a final little crunch and nutty perfume. Serve immediately over warm rice for contrast in temperature and texture. Watch out for leaving it on residual heat which continues to cook the components, potentially making them dull and soft.