Cut chicken into bite sized pieces.
Heat 3 tablespoons of oil in a wok or large skillet and over high heat, when the oil is hot, add chicken, stir often, cooking until chicken is cooked through but not browned. Remove to a bowl and set aside.
Add 3 tablespoons oil to the wok and place over high heat. When the oil is hot, add onion, bell peppers, carrots and broccoli. Cook stirring often about 3 minutes, stir in mushrooms and continue to cook 5 minutes.
Mix in minced garlic, cooking about 2 minutes.
Next, add chicken into the vegetables and mix well.
Mix the sauce in a small bowl by combining the brown sugar and cornstarch. Add orange juice, soy sauce, sesame oil and ground ginger. Whisk to combine.
Pour sauce over the chicken and vegetables, stir occasionally, cooking until sauce is thickened, about 5- 10 minutes.
Remove from heat.
Serve chicken stir fry over cooked rice and garnish with sesame seeds.