Prep the chicken: Trim and cut the chicken into bite-sized pieces. Pat dry with paper towels so it sears a bit in the slow cooker’s heat and doesn’t water down the sauce.

Make the sauce: In a bowl, whisk soy sauce, chicken broth, rice vinegar, sesame oil, brown sugar (or honey), garlic, ginger, and a pinch of red pepper flakes or sriracha if you like heat.

Load the slow cooker: Add the chicken and onion to the slow cooker. Pour the sauce over and stir to coat evenly.

Cook the chicken: Cover and cook on Low for 3–4 hours or High for 1.5–2 hours, until the chicken is just cooked through and tender. Avoid overcooking; chicken dries out if left too long.

Add the veggies: Stir in bell peppers, broccoli, carrots, and peas. Cover and cook on High for 30–45 minutes, until the vegetables are crisp-tender.

Thicken the sauce: In a small cup, stir cornstarch with 2–3 tablespoons water to make a slurry. Pour into the slow cooker and stir well. Cook on High for 10–15 minutes more, until the sauce thickens and coats the chicken and vegetables.

Taste and adjust: Add a splash more soy for salt, a drizzle of honey for sweetness, or a squeeze of lime for brightness. Stir in sesame seeds and sliced green onions if using.

Serve: Spoon over hot rice or noodles. Finish with extra chili sauce if you like it spicy.