Dissolve a fish stock cube and a vegetable stock cube in two pints of boiling water in a large saucepan. Add a stick of lemongrass (preserved from a jar is fine), a few dried Kaffir Lime leaves, and a teaspoon of Thai fish sauce.
Then roughly chop up a whole lime (just wash the outside and hack into lumps!) and add the whole thing to the broth. Bring back to the boil, then cover and simmer gently for at least twenty minutes.
While the broth is simmering, fill another large saucepan with water and bring to the boil. Once at a rolling boil, chuck in 4 ounces of rice noodles (there are various kinds and thicknesses, all good) and cook for a couple of minutes (or whatever it says on the packet!). Drain in a sieve.
With a slotted spoon, remove the lime, kaffir leaves and lemongrass from the broth and discard. Bring back to the boil and add a couple of spring oinions (chopped), a couple of small hot red chillis (more or less depending on how spicy you like your food!) and a small piece of ginger (about half and inch on a side), very finely sliced. Also add a good handful of fresh coriander leaves - or dried if you must.
After a few minutes, add the drained noodles, stiring gently to distribute them evenly. Once thoroughly re-heated, split broth and noodles into two large bowls. Top the noodles with chicken or fish cooked separately - Teriyaki Tuna or Chicken Teriyaki both work well - and a few pieces of cucumber, finely sliced length-ways. Serve immediately.
I'm told this dish is traditionally eaten with chopsticks and a wooden spoon, although a metal one works fine.