Cut the beef brisket and enoki mushrooms into bite-sized pieces.
Slice the green onion and cut the garlic into thin slices.
Heat cooking oil in a pan, then stir-fry the green onion and garlic to release their aroma.
Add the beef brisket and stir-fry quickly over high heat.
When the beef is partially cooked, add the enoki mushrooms.
Season with soy sauce, salt, and black pepper while stir-frying.
Once the mushrooms are wilted, turn off the heat and serve on a plate.