Spicy sour beef with tamarind sauce (sam-loh machu kroeung sach koh)

In Cambodia, Chinese water spinach, apple eggplants and cabbage are traditionally the vegetables used in this dish, but in Australia, depending on the season, Liep also uses cauliflower or broccolini. A Cambodian herb called mreh prov is sometimes used, too, lending the dish a mild citrusy flavour, but as it is only available in summer from a few Asian greengrocers, we have omitted it.