Marinate the steak by mixing soy sauce, mirin, and cornstarch in a bowl. Toss the beef to coat and let it rest for 10-15 minutes.
In a separate bowl, whisk together beef broth, soy sauce, honey, oyster sauce, and cooking wine. Set aside.
Heat 1 tbsp oil in a large pan over high heat. Add steak in a single layer and cook for 30-45 seconds without stirring until browned. Flip and cook for another 30 seconds. Remove the steak and set aside.
Return the pan to medium heat and add the remaining oil. Stir-fry the onions and peppers for about 4 minutes until softened. Add garlic and ginger, cooking for 30 seconds.
Stir in the sauce and bring it to a simmer for 1 minute until it thickens.
Return the steak to the pan, stirring to coat it with the sauce. Cook for 30 seconds, then remove from heat.
Serve your delicious steak over rice or noodles, garnished with scallions and sesame seeds if desired!