Home made Thai hot and sour soup (tom yum) is not terribly difficult to make – a good stock plus aromatics including ginger, garlic, lemongrass, galangal, some fresh and/or chiles, and prawns (tom yum goong), fish (...talai), chicken (...gai), a splash of fish sauce, and you're all set. But a spoonful of this concentrate plus a cup of boiling water and a bit of this and that will make a surprisingly tasty and quick alternative. Great for the lunch room. (Add some rice noodles, which don't require cooking, or unflavoured instant noodles for a heartier version.)