1 large onion
2 cloves garlic
2 carrots
1 potato
1 tablespoon lentils
1 tablespoon pearl barley
Any other vegetables you happen to have handy
Salt, pepper, herbs, etc.
About 2 pints vegetable stock (from a cube or, better, Marigold Bouillon)
Peel vegetables where appropriate and chop roughly - no need to cut finely. Boil everything together in a pressure cooker for about 20 minutes - or in a regular saucepan for an hour or so. Then puree in a food processor or blender, or rub through a sieve. Return to stove, and simmer gently for as long as possible - you might like to add frozen peas and/or sweetcorn, soup pasta or rice at this stage. Stir every so often so it doesn't stick.
You can, of course, use chicken stock in place of vegetable, if you are not vegetarian. To make your own chicken stock, boil the chicken carcase in 2 pints of water in the pressure cooker for about 30 minutes, strain, leave to get cold, refrigerate overnight. The next morning, pick off the layer of fat that has solidified on the top.