Slice steak into thin 5cm strips. In a pan, heat half the oil and stir-fry beef for 1 minute, then remove from pan.
Heat remaining oil and sauté spring onions and bamboo shoots for 3 minutes. Add salt and fish sauce and cook, stirring, for 5 minutes. Add garlic and cook for further 2 minutes.
Return steak to pan and cook until just tender. Remove from heat, add sesame seeds, stir through and serve.