h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Collect :- an onion, some potatos, milk and/or stock, caraway seeds, salt and pepper.

Chop onion and saute till soft.
Chop potatoes into little cubes, add to pan and stir around for 5 minutes or so. Add remaining ingredients, simmer for 20 minutes.
Blend mixture to required consistency, reheat and serve.

For variety add leeks or parsnips or whatever else is lying sadly neglected in your vegetable rack.

At the risk of putting Metal Chicken off his/her food, here's a few more details......

While it might take the bluest of moods to make you sit down to a plate of plain mashed potatoes for dinner, a bowl of potato soup tells a more cheerful story. You still have the comforting mellow earthiness and finely grained texture of mashed potatoes, but the flavour grows in depth and complexity with the addition of simple winter ingredients such as onions, garlic, bayleaf, cream, kale, celery or smoked fish.

Choose one of the same potato varieties you would use for mashed potato. If retailers are doing their job properly, these will be labelled floury or all-purpose potatoes.

You don't need to use stock when you make potato soup, particularly if you include plenty of onions and garlic but it does deepen the flavour. Use enough liquid to barely cover the potatoes and thin the soup down after it has been pureed, This is easier than trying to thicken up soup that is too thin. Milk or cream will enrich the flavour and smooth out the texture.

A mouli is still the best tool for producing a smooth soup without lumps, but a hand-held processor wand is irresistibly convenient for most occasions. Use the wand in short bursts while moving it around the pot, so that the potato is pureed in as short a time as possible. This minimises the risk of the potato turning to glue. Using this basic recipe and its variations as a guide, you can build up a repertoire to last all winter long. You need to use one medium potato for each serving.

POTATO SOUP WITH HERBS
2 tbsp butter
1 large onion, finely sliced
2 cloves garlic, finely sliced
3 medium-sized floury or all-purpose potatoes, peeled and finely sliced
salt, pepper and a little cayenne
1 small bayleaf
water or chicken stock
milk or cream soft green herbs, such as parsley, dill, chervil, chives

Melt the butter in a heavy pot and add the onion and garlic. Cook very gently, stirring occasionally, for several minutes until the onion is pale gold. Add the sliced potatoes and continue to cook until they start to stick to the bottom of the pot, but have not started to colour. Season with salt, pepper, cayenne and the bayleaf and add enough water or stock to cover the potatoes. Cover the pot and simmer until the potatoes are very tender and starting to break up. Remove the bayleaf and puree the potatoes in the pot with a wand processor, or put the contents of the pot in a bowl processor, or use a mouli or ricer. To thin down the soup to the right consistency, add extra water, stock, milk or cream. Reheat, taste and adjust the seasoning. just before serving, stir in finely chopped soft green herbs. Ladle into heated bowls and serve with toast or croutons.
Serves 3.

Oops, I missed a line-break. The last part of the ingrediant list should look like this...

water or chicken stock
milk or cream
soft green herbs, such as parsley, dill, chervil, chives

And here are a few variants. Yes, winter is rapidly approaching in New Zealand

POTATO SOUP WITH ROASTED GARLIC
Put the garlic on to roast before you start the soup. Preheat the oven to 190 degree C. Take 2 whole heads of good-quality garlic, put them on a chopping board and slice across the tips to expose the inside of each clove. This will make it easier to squeeze out the cooked garlic after it has been roasted. Put the heads of garlic on a double thickness piece of aluminium foil, pull up the edges of the foil and sprinkle with a little olive oil and water. Seal the package and put in the oven for about 30 minutes, when the aroma of roasted garlic will start to escape from the oven. Take the package out, unwrap and check that the garlic cloves are very tender when tested with a skewer. Set aside to cool a little. When the potatoes are ready to be pureed, use your hand to squeeze the roasted garlic into the pot, then puree. Adjust the consistency and seasoning, ladle the soup into bowls and trickle a little fine olive oil over the top of the soup.

POTATO SOUP WITH GARLIC AND WINTER GREENS
Roast garlic heads as described above and add to the soup. When the soup is almost ready, take a bunch of winter greens, such as kale, savoy cabbage, watercress or tender silverbeet. Blanch the leaves in boiling salted water, then drain, refresh with cold water, squeeze dry with your hands, and chop. Add to the soup after it has been pureed. Trickle each bowl with olive oil or add a knob of butter.

POTATO AND LEEK SOUP
For this old favourite, follow the basic recipe, using a small onion and adding the finely sliced white and pale-green parts of 1 or 2 leeks. Use chicken stock as the liquid. After the soup has been pureed and thinned down, enrich with a little cream.

POTATO SOUP WITH SMOKED FISH AND PARSLEY
Steam a 300g fillet of a smoked white-fleshed fish and pull off the skin. Add the flakes of fish to the soup after it has been pureed. Season the soup with a little curry powder and lots of finely chopped parsley.