In a pan, melt 2 tablespoons of butter over medium heat. Add the minced garlic and cook, stirring frequently, until golden brown and crispy, about 2-3 minutes. Be careful not to burn the garlic. Once done, remove the garlic from the pan and set aside for later use as a topping.

In the same pan, heat a little oil over medium-high heat. Add the thinly sliced beef and sauté with oyster sauce, soy sauce, mirin, and freshly cracked black pepper. Cook until the beef is browned and tender, about 5-7 minutes. Remove the beef from the pan and set aside.

In the same pan, melt 2 tablespoons of butter over medium heat. Add the chopped onions and sauté until soft and translucent, about 3 minutes. Add the sliced mushrooms and cook until they’re golden brown and have released their moisture, about 5 more minutes.

Pour in the soy sauce and sprinkle with black pepper. Add a splash of water to help the sauce come together. Let it simmer for 2-3 minutes to allow the mushrooms and onions to absorb the flavors.

Gradually sprinkle in the flour while stirring constantly to avoid lumps. Continue stirring until the sauce thickens to a smooth consistency. If the sauce becomes too thick, add a bit more water to loosen it up.

Return the sautéed beef to the pan with the mushroom and onion sauce. Stir everything together, letting it simmer for an additional 2-3 minutes to blend the flavors.

Transfer the Garlic Pepper Beef with Mushrooms and Onions to a serving dish. Generously top the dish with the crispy minced garlic for added crunch and flavor. Serve hot over steamed rice and enjoy!