Prepare the ingredients by slicing beef and mincing garlic and ginger.
Soak the flat rice noodles in hot water until softened, then drain.
In a bowl, mix together soy sauce, oyster sauce, brown sugar, and cornstarch to create the sauce mixture.
Heat a tablespoon of oil in a large pan over medium-high heat and sauté the garlic and ginger until fragrant.
Add the sliced beef to the pan and stir-fry until browned and cooked through.
Pour the sauce mixture over the cooked beef, stirring to coat evenly.
Add the soaked noodles to the pan and toss everything together, ensuring the noodles are fully coated in the sauce.
Finish with green onions and a drizzle of sesame oil before serving.