Heat the cooking oil in a large skillet over medium heat and add the minced garlic. Cook until golden brown and crispy, about 2-3 minutes. Using a fine mesh strainer, separate the crispy garlic from the oil and set the garlic aside for garnish.
1 1/2 heads garlic, 1/4 cup cooking oil
Reduce the garlic oil to 2 tablespoons in the pan. Increase heat to medium-high and sauté the sliced beef until it browns on all sides, about 4-5 minutes total.
1 1/2 lbs beef sirloin
Pour in the soy sauce and oyster sauce, then season with salt, ground black pepper, and half of the toasted garlic. Stir to combine and cook for 1 minute. Remove beef from pan and set aside.
2 tablespoons soy sauce, 3 tablespoons oyster sauce, 1/2 teaspoon ground black pepper, 1/4 teaspoon salt
In the same pan, melt the butter over medium heat. Add the flour and whisk continuously, cooking until the mixture turns golden brown, about 2-3 minutes.
3 tablespoons butter, 4 tablespoons all-purpose flour
Gradually pour in the beef broth while whisking constantly to prevent lumps. Add the sliced mushrooms and bring to a simmer. Stir until the sauce thickens, about 3-4 minutes, then season with onion powder, garlic powder, salt, and ground black pepper.
14 oz button mushrooms, 1/2 teaspoon onion powder, 1/4 teaspoon garlic powder, 1/8 teaspoon ground black pepper, 1 3/4 cups beef broth, salt
Add the cooked beef back to the pan and toss until well combined with the mushroom gravy. Cook for 2-3 minutes to heat through. Transfer to a serving plate, top with the remaining crispy garlic, and serve immediately.