It's a simple recipe:
10 Onions, sliced
6 Beef Oxo Cubes
1tbsp Garlic Powder
6ltrs Water
2tbsp Butter
Fry the Onions in the butter until slightly golden, add the remaining ingredients, stir, bring to the boil and then simmer for 1 hour.
When serving drop a piece of thin toasted bread on top of the hot soup along with a generous amount of grated cheese and either leave to melt or grill for a short time until melted and bubbly!
Looks like this: http://www.flickr.com/photos/stripypixi ... 548978150/
Tastes like heaven

Edit: Oh and because we buy sacks of Onions for very little money it probably costs about 25p per bowl of soup so cheap too!