Whisk together all marinade ingredients and pour over sliced flank steak in resealable bag. Marinate in the refrigerator at least 1 hour.
Cook rice according to package directions.
Heat 1 tsp sesame oil over high heat. Add garlic, ginger, red pepper flakes and sauté until fragrant.
Add broccoli and carrots to sautéed garlic and toss. Add water. Cover with a lid for 2-3 minutes until broccoli turns bright green and is tender crisp. Set broccoli aside in a bowl.
Add olive oil to pan and heat until very hot. Add beef and sauté while tossing for 4-5 minutes until almost cooked. Add sauce and continue to stir and cook for 2-3 minutes as sauce boils and thickens and steak cooks through.
Remove from heat and toss with broccoli mixture. Serve over top of rice and garnish with sesame seeds and sliced green onions if desired.
Be sure to check the label of your oyster sauce to make sure it doesn't contain MSG!