In a bowl, toss chicken with soy sauce and cornstarch. Let marinate 5 minutes.
Heat 1 tbsp oil in a wok or large skillet over high heat. Add chicken and stir-fry until golden and cooked through, about 3-4 minutes. Transfer to a plate.
Add remaining 1 tbsp oil to the wok. Add bell peppers, broccoli, and carrot; stir-fry 2-3 minutes until crisp-tender.
Add garlic and ginger; cook 30 seconds until fragrant.
In a small bowl, whisk together chicken broth, oyster sauce, rice vinegar, and sesame oil. Pour into the wok and bring to a simmer.
Return chicken to the wok. Toss everything to coat in sauce and heat through, about 1 minute.
Serve immediately over steamed rice, garnished with sesame seeds and green onions.
Tips
For extra heat, add a pinch of red pepper flakes with the garlic.
Substitute chicken with tofu or shrimp if desired.
Leftovers can be stored in an airtight container in the fridge for up to 2 days.