Prepare the noodles according to instructions on the packaging.
Cut the beef into thin strips.
Heat the sesame oil in a wok or a large frying pan. Add the garlic and ginger and fry for about a minute. Add the beef and cook for another 2 minutes. Next, add the leeks, pepper and mushrooms and fry for about 5 minutes.
Finally, add the cooked noodles, season with pepper and a pinch of sugar. Pour in the soy sauce and water, then stir and fry for another 2 minutes.
To serve, divide onto serving dishes and garnish with chopped spring onions.