2 flank steak (around 2 lbs), cut into 1/4-inch thick slices
6 tbsps soy sauce
2 tbsps cornstarch
2 tbsps brown sugar
3 tbsps sesame oil
2 tbsps mirin
1/2 tsp red pepper flakes
3 to 4 cloves garlic, minced
3 tbsps vegetable oil
1 medium onion, cut into 1-inch pieces
1 red bell pepper, cut into strips
1 green bell pepper, cut into strips
In a bowl, combine soy sauce, mirin, brown sugar, sesame oil and red pepper flakes. Stir until smooth. Toss in beef slices to coat and set aside.
In a wok or wide skillet, heat half of the vegetable oil until smoking hot, over high heat.
Stir-fry bell pepper strips until tender but crisp. Remove and set aside.
Stir-fry onions until softened, about 3 minutes.
Add the remaining oil to wok and and heat for 30 seconds.
Saute garlic for around 30 seconds.
Drain beef slices from marinade, reserving liquid mixture. Stir-fry beef slices on wok until well browned.
Add in onions, bell peppers, reserved marinade and any accumulated juices to wok.
Cook until heated through.
Serve over hot rice.