Marinate the Steak: In a bowl, combine soy sauce, sesame oil, mirin, rice vinegar, garlic, ginger, and black pepper. Toss the steak cubes in the marinade and let them rest in the refrigerator for at least 30 minutes, ideally 1 hour for maximum flavor.

Prepare the Yum Yum Sauce: Mix mayonnaise, ketchup, rice vinegar, sugar, paprika, and water until smooth. Refrigerate while the rest of the meal cooks. This can be made ahead for better flavor.

Cook the Fried Rice: In a large skillet or wok over medium-high heat, melt butter. Add the diced onions and sauté for 2 minutes. Push the onions to one side and pour in the beaten eggs. Scramble until just cooked, then mix everything together. Add the rice, peas and carrots, and stir-fry for about 5 minutes. Season with soy sauce, oyster sauce, garlic powder, and finish with a drizzle of sesame oil. Stir well and set aside.

Sauté the Vegetables: In the same skillet, heat vegetable oil over medium heat. Add onions, zucchini, bell pepper, and mushrooms. Stir-fry for 4–5 minutes until tender-crisp. Add soy sauce and teriyaki sauce, toss to coat, and remove from heat.

Sear the Steak: Heat a clean skillet or grill pan over high heat. Add a splash of oil if needed. Sear the marinated steak cubes for 2–3 minutes per side, until browned on the outside and cooked to your preferred doneness inside. Avoid overcooking to keep the steak tender and juicy.

Assemble the Bowls: Scoop a generous serving of fried rice into each bowl. Top with sautéed vegetables, followed by the steak bites. Drizzle with Yum Yum Sauce or serve on the side.