Heat the oil over moderate heat in a wok or frying pan. Add the curry paste and fry gently for 5 minutes.
Turn up the heat and add the sliced steak. Stir-fry until it just colours then add the beans and stock.
Bring to the boil, mix well and add the coconut cream, lime juice, fish sauce and sugar.
Mix well, taste and adjust the sweet, salty and sour flavours if necessary.
Serve on steamed rice with coriander sprigs and sliced tomatoes and cucumber.