Rub the steaks with a little fish sauce, salt and pepper. Heat the oil in a large pan and fry the steaks for 2-3 minutes on each side or until they are cooked to the desired degree.
Remove the meat from the pan and let it rest for 5 minutes, then cut it into thin slices across the fibre, catching the meat juice. If you prepare the salad in advance, cut the steaks just before serving.
Mix steak slices and meat juice in a serving bowl with cucumber, onion rings, spring onions, tomatoes and herbs.
Mix the chilli sauce with the lime zest, lime juice and 2 teaspoons of fish sauce and dress the salad with it. If it is to be served as a main course, steamed rice is suitable as a side dish.