Remove the skin from the garlic and chop finely, stir through with the sesame oil and soy sauce. Cut the beef fillet into fine slices and turn to the other side in the marinade.
Pour hot water over the glass noodles, swell. Drain the ginkgo noodles. Slit the leek, rinse, cut into tender strips.
Heat the oil in a hot wok (or hot deep frying pan) not too high, stir-fry the beef. Fill up with the clear soup, let it bubble up, pour in nuts, leek.
Boil briefly, season before serving.