One of the culinary delights available on Fisherman's Wharf in San Francisco is fish soup served in a sourdough roll. The idea also pops up here and there round the world as there's nothing very difficult about it, and it turns a humble soup into a special, fun eating experience.

In the picture above the roll is filled with white borscht, a Polish soup made with kielbasa sausage (pork with garlic and marjoram), hard-boiled eggs and potatoes. The recipe is entirely flexible and depends on what is available. The important thing is to make a thick soup, to delay the time it takes for it to leak through the roll and onto the diner's lap. Potatoes are a good base for any thick soup; one of my favourites is leek and potato, that staple of cold winter days in northern latitudes. You could have a Mediterranean theme with a thick fish soup. The variations are vast.

As for the rolls, it's obviously best to pick a bread that's fairly dense and leak-proof. Sourdough is a very American product but many Italian rolls are good for this too. The outside of Italian bread tends to be quite hard and dry, so what better than to hollow out the soft content in the middle and replace it with thick soup? Don't forget to take off the "lid" of the roll-based soup bowl carefully so it can be replaced before serving.

As for the occasion, well it's probably safer to serve this kind of meal outdoors, as accidents can have the hot contents of the roll seeking the nearest exit in a downward direction. Soups are winter food so the early spring is just right to feed a garden working party, for example.

You can use the the contents of the roll to make croutons or use as bread crumbs for another dish.