Start by preparing all your ingredients so cooking flows smoothly. Cut the chicken into 1-inch bite-sized chunks and set aside. In a small bowl, whisk together the soy sauce, sake, mirin, sugar, and freshly grated ginger until the sugar dissolves completely. Set the sauce aside. Finely shred the cabbage, dice the carrot and capsicum, and mince the parsley. I find having everything prepped before the pan heats up makes the cooking process much less stressful and allows you to focus on getting the chicken perfectly glazed.
Heat a large skillet or wok over medium-high heat until it's hot but not smoking. Add the chicken chunks in a single layer, working in batches if needed to avoid crowding the pan. Let them cook undisturbed for 3-4 minutes until the bottoms develop a golden-brown color and the chicken releases easily from the pan. Flip the pieces and cook for another 2-3 minutes until mostly cooked through. The goal is to get a flavorful caramelized exterior while keeping the inside tender—don't worry if it's not completely cooked through yet, as it will finish cooking in the glaze.
Pour the teriyaki sauce mixture from Step 1 directly into the pan with the seared chicken. Reduce the heat to medium and cover the pan for about 30 seconds to let the sauce warm through. Remove the lid and continue cooking, stirring occasionally, for 2-3 minutes until the sauce reduces and becomes thick and glossy, coating the chicken beautifully. I like to watch for the sauce to visibly cling to each piece—that's when you know the glaze is ready. Once the sauce has thickened, remove the pan from the heat and let it rest for 1-2 minutes so the chicken can fully absorb the flavors.
Arrange the shredded cabbage on a serving plate as your base. Top with the teriyaki-glazed chicken and drizzle any remaining sauce from the pan over the top. Scatter the diced carrot and capsicum around the plate, then sprinkle with the toasted sesame seeds and minced parsley for a fresh, bright finish. Serve immediately while the chicken is still warm and the glaze is at its most flavorful.