In a bowl, toss chicken with soy sauce and cornstarch until coated.
Heat 1 tbsp oil in a wok or large skillet over high heat. Add chicken and stir-fry until golden and cooked through, about 4 minutes. Remove and set aside.
Add remaining 1 tbsp oil to the wok. Add bell peppers and broccoli; stir-fry for 2 minutes.
Add garlic and ginger; cook for 30 seconds until fragrant.
In a small bowl, whisk together chicken broth, oyster sauce, brown sugar, and sesame oil. Pour into the wok and bring to a simmer.
Return chicken to the wok. Toss everything together and cook for 1-2 minutes until sauce thickens slightly.
Serve immediately over cooked rice.
Tips
Feel free to substitute vegetables like snap peas, carrots, or mushrooms.
For extra heat, add a pinch of red pepper flakes with the garlic.
Leftovers can be stored in an airtight container in the refrigerator for up to 3 days.