Ketchup (catsup) has an interesting history. The Chinese tradition of using the brine from pickled fish as a dipping sauce (“ke-tsiap”) was transferred to England by sailors in the late 17th century. The English adapted the recipe first to use the brine from pickled walnuts, then to be based mainly on mushrooms; and finally after a fair bit of American influence, tomato ketchup became the primary form of ketchup used in the UK around the end of the 19th century.
This is not a thick ketchup as you'd normally understand it. It's a thin, richly-flavoured sauce that makes an excellent ingredient wherever you want a bit of extra mushroom oomph. It was highly popular among the Victorians, though they mainly used it as a sauce with meat. Try it in my Simple Mushroom Rice recipe.
The following recipe is adapted from one found in the Victorian Gamer (careful — that link starts off with a meat recipe; the mushroom ketchup is at the bottom).
Makes two jam-jars full (will measure properly next time).
Chop the mushrooms then puree them in a blender. Mix in the salt, then leave in a covered bowl in the fridge for two or three days, stirring at least once a day. The mixture should slowly turn black, starting from the exposed surface, and the mushrooms should give off liquid.
Empty the mushroom puree and its juices into a saucepan. Add the spices and port, and simmer for 5 minutes. Push through a sieve, keeping what goes through and discarding the solids left in the sieve. Store in sterilised jars in the fridge. I've had it keep for months, but this is at your own risk. I'm sure it would freeze well.
Kake's (Vegan) Cookery Site - http://www.earth.li/~kake/cookery/
This page added 17 October 2003 - comments and questions to Kake L Pugh (email@example.com).