In a bowl, toss chicken with soy sauce and cornstarch. Let marinate 10 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 4 minutes. Remove and set aside.
Add remaining 1 tbsp oil to the wok. Add broccoli and stir-fry 2 minutes, then add garlic and ginger; cook 30 seconds.
Return chicken to the wok. Add chicken broth, oyster sauce, sesame oil, and red pepper flakes. Stir-fry until sauce thickens, about 1 minute.
Season with salt and white pepper to taste. Serve immediately over rice.
Tips
For extra crunch, blanch broccoli in boiling water for 1 minute before stir-frying.
Substitute chicken with beef or tofu if desired.
Store leftovers in an airtight container in the refrigerator for up to 3 days.