Mix the soya sauce, rice wine, olive oil, chilli flakes and black pepper together. Pour over the beef and marinate for at least one hour, preferably overnight in the fridge.
Make the dressing. Combine the lime juice, sugar, 25ml water, fish sauce, chilli, lemon grass, corriander root and garlic.
Lay out a serving platter and cover with shredded lettuce, spinach and rocket leaves.
Put two bundles of fine rice noodles into boiling water and leave for 5 minutes, then drain when tender.
Sear the beef in a hot pan or on a bbq and cook until browned all over and pink in the middle. Baste with the marinade regularly. Cut into slices and let rest for 5 minutes.
Put the drained noodles over the salad. Layer the beef slices on top. Cover with finely sliced red onion and dress with the dressing. Sprinkle with corriander leaf and serve immediately.