Creating the High-Protein Steak and Shrimp Stir-Fry is simple if you follow these easy-to-follow steps:

1. Marinate the Steak: In a bowl, combine sliced flank steak, soy sauce, oyster sauce, and sesame oil. Let it marinate for about 10 minutes.
2. Prepare the Shrimp: While the steak marinates, season the shrimp with salt and pepper. Set aside.
3. Prepare the Vegetables: Slice the bell peppers and onion, and cut the broccoli into small florets. Mince the garlic and ginger.
4. Heat the Pan: In a large skillet or wok, heat vegetable oil over medium-high heat.
5. Cook the Steak: Add the marinated steak to the hot pan and stir-fry for about 3-4 minutes, until browned and cooked to your liking. Remove from the pan and set aside.
6. Stir-Fry the Shrimp: In the same pan, add the shrimp and cook for 2-3 minutes until they turn pink. Remove and set aside with the steak.
7. Sauté the Vegetables: Add a little more oil if needed, then add garlic, ginger, onion, bell peppers, and broccoli to the pan. Stir-fry for about 4-5 minutes until the vegetables are tender-crisp.
8. Combine Ingredients: Return the steak and shrimp to the pan. Toss everything together until well combined.
9. Thicken the Sauce: In a small bowl, mix cornstarch with a bit of water to create a slurry. Stir this into the pan to thicken the sauce.
10. Serve Hot: Garnish with sesame seeds and green onions, if desired, before serving.

Following these straightforward steps will help you create an impressive High-Protein Steak and Shrimp Stir-Fry that everyone will love.