It honestly takes less than 5 minutes from turning on the kettle to sitting at the table.
This is the bog standard, basic staple recipe which you can jazz up with spring onions, prawns, leftover chicken breast, mushrooms, baby corn, strips of fresh ginger, basically anything you happen to have leftover. Believe me though, this version is beautiful just as it is and also very filling.
In a small saucepan put 2 tablespoons liquid chicken stock, 1 tablespoon Thai fish sauce, juice of 1 lime, 1 small red chilli, snipped in, a handful of ripped coriander, also snipped in and 1 tablespoon Tom Yum soup paste (if you don't have any you can leave this out and just make it with the rest of the ingredients. This turns it into a standard hot and sour soup instead of a Tom Yum soup but it is still just as nice). You can also add a small pinch of brown sugar if you want to tone down the sharpness a little but remember, this soup is supposed to be hot and sour, not sweet.
Pour the boiling water on the top and bring to a rapid boil.
Add your choice of noodle (egg or vermicelli are my favourites) plus anything else you want to throw in.
Boil for about 3 minutes and serve.