In a mixing bowl, combine diced chicken breasts with sesame oil, soy sauce, hoisin sauce, minced garlic, and fresh ginger. Stir well to ensure the chicken is evenly coated. Let this mixture marinate for at least 15 minutes at room temperature.

Heat a large skillet over medium-high heat for about 2 minutes until hot. Add the marinated chicken to the skillet in a single layer, cooking for approximately 10 minutes, or until golden brown and fully cooked.

In the same skillet, pour in a splash of olive oil and heat it over medium-high heat. Add the sliced onions, carrots, mushrooms, and zucchini. Sauté for about 5 minutes until tender-crisp.

Push the sautéed vegetables to the side, melt butter in the open space. Add minced garlic and sauté for 30 seconds. Stir in cooked rice and a splash of soy sauce. Create a well in the center, crack in an egg, and scramble it.

To serve, layer fluffy fried rice, sautéed vegetables, and juicy chicken. Optionally drizzle with mustard sauce for added flavor.