In a small bowl, mix the cornstarch and water to create a slurry; set aside.
Heat the vegetable oil in a large skillet or wok over medium-high heat.
Add the sliced chicken to the skillet, season with salt and pepper, and cook for 5-7 minutes, or until browned and cooked through. Remove the chicken from the skillet and set aside.
In the same skillet, add the minced garlic and grated ginger, and sauté for about 30 seconds until fragrant.
Add the mixed bell peppers, broccoli, and carrots to the skillet. Stir-fry the vegetables for about 4-5 minutes or until they are tender-crisp.
Return the cooked chicken to the skillet. Drizzle the soy sauce and sesame oil over the mixture. Stir everything together to combine well.
Pour the cornstarch slurry into the skillet and stir to thicken the sauce, cooking for an additional 1-2 minutes.
Remove from heat and garnish with sesame seeds.
Notes
Serve over rice or noodles and garnish with sesame seeds and fresh herbs.