Chinese Egg Soup
Make half a pint of vegetarian stock - I use Marigold powdered bouillon, or Kallo stock cubes, or yesterday's vegetable cooking water, or sometimes I just use plain water. If you're not vegetarian use an Oxo cube or chicken Bovril. Add a slug of soy sauce and bring to the boil. Stir your boiling stock vigorously and slowly pour a beaten egg into it, stirring all the while. It will set into long fine strands when it hits the water. Add some bean sprouts (or sweetcorn, finely chopped spring onion, chives, parsley, whatever you've got) and serve.
It takes the same amount time as making a cup-a-soup, but it's a lot nicer and better for you.