Marinate the chicken: In a bowl, mix the cubed chicken breasts with teriyaki sauce, minced garlic, and ginger. Allow it to soak for a minimum of 15-20 minutes as you get the remaining ingredients ready.
Cook the chicken: Warm the olive oil in a frying pan on medium heat. Add the marinated chicken and cook for 6-8 minutes until fully cooked and browned. Set aside.
Prepare the stir fry: In that same frying pan, add the sesame oil and heat it over medium. Add the mixed vegetables and sauté for 3-5 minutes until they’re crisp-tender. Stir in the cooked rice and sliced green onions. Season with salt and pepper to taste.
Assemble the casserole: Preheat your oven to 375°F (190°C). In a large baking dish, spread the cooked stir-fried vegetables and rice evenly. Layer the cooked teriyaki chicken over the vegetables.
Add the topping: Sprinkle the shredded cheese over the top of the chicken and vegetables. If you like, sprinkle sesame seeds for garnish.
Bake the casserole: Place in the preheated oven for 15-20 minutes, or until the cheese is melted and has a bubbly appearance.
Serve and enjoy: Remove the casserole from the oven, let it cool for a few minutes, and serve warm. Garnish with extra green onions or sesame seeds if desired.