Mushroom ketchup: not as expensive as you think

This post is all about my attempt at one of the signature flavours of the 18th century: mushroom ketchup.  Mushroom ketchup was to the 18th century what garum was to the Romans, an all purpose flavouring agent used in a wide variety of dishes, and in fact the taste is not unlike fish sauce.  It's a salty, savoury, umami flavour.

Due to the popularity of mushroom ketchup, historical recipes tended to assume you were making the stuff in industrial quantities, which is prohibitively expensive for most of us today.  But do you, as a modern cook, actually need an industrial sized bucket of mushroom ketchup?  In this post I'm going to make a smaller, affordable quantity of this ketchup using about 500 grams of mushrooms.  If you do need a large quantity of it, here is an awesome cheat recipe made with mushroom bouillon.

Recipes for mushroom ketchup varied, but they all followed the same basic pattern.  You salted your mushrooms and left them to sit for a while so the salt could draw out the mushroom liquor, then you squeezed all the liquor into a pot, boiled it with spices, and strained it again into bottles.  Some cooks added wine or ale, but this was apparently optional, and the spices involved varied.

Here is a recipe from Hannah Glasse's The Art of Cookery.

And here is John Farley's version from The London Art of Cookery.  The similarity in titles, by the way, was probably not accidental.  Farley seems to have "borrowed" a lot from Hannah Glasse, who herself plagiarized earlier authors.

At least one recipe requires the salted mushrooms to be placed in a low oven for 24 hours, but I don't care to leave the oven on for a full 24 hours with no one to watch it while I sleep and go to work and besides, not all recipes included this step, so I just put my casserole dish full of mushrooms next to the hot water cylinder.  Note that I have chopped my mushrooms to make them easier to squeeze.

Here is what I ended up with.  At this point the mushrooms have been sitting for a full 24 hours and have released an amount of juice which, frankly, surprised me because I had expected some liquid to be visible, but as you can see there's none.  They smelled good though, so there's that.

Maybe this is why John Farley says to leave the salted mushrooms for four days, and maybe Hannah Glasse didn't say to heat the mushrooms because her audience already knew that.  But my mushrooms weren't looking good.  Hmmm.  What if I zapped them in the microwave?  Microwaving things makes them soggy, right?

Now we're getting somewhere!  In this picture they've been microwaved for five minutes.

I microwaved my salted mushrooms for one minute at a time on medium power, about fifteen minutes in total.  I took them out to check their progress after each minute and kept going until there was a lot of liquid in the dish and the mushroom pieces were soft.

It seems you do need to heat the mushrooms in order to extract their liquor, but you can totally cheat and use a microwave.

Here's my modernized version of Hannah's mushroom ketchup recipe.  For around 200 mls of ketchup you will need:

500 grams mushrooms
About 2 tablespoons of table salt (it doesn't need to be exact)
1 teaspoon whole peppercorns
1/8 teaspoon ground cloves
1/8 teaspoon ground mace
1/8 teaspoon ground ginger

Clean your mushrooms, remove the stalks, and chop them.  Layer them in a pan with the salt sprinkled over them and leave them somewhere warm until they're soft and sitting in a nice pool of mushroom liquor or, y'know, help them along in the microwave.

Squeeze all the mushroom liquor into a saucepan using a cloth.  This will take a lot of squeezing, and you will be able to extract a lot more liquor than you think.  Don't throw the squeezed mushrooms away, you can dry them completely and use them for cooking.

Add the spices to your saucepan and simmer it, covered, for 15 minutes, then cool it and strain it into a bottle.  The ketchup will be watery, and that's okay.  It's a concentrated flavouring not a sticky condiment.  You add small quantities of it to boost the flavour of stews and gravies.

If you have a whole kilo of mushrooms (try the farmers' market), it's worth doubling this recipe because it is labour intensive and trust me, you will find plenty of uses for mushroom ketchup.  It's delicious.  There's a reason people in the 18th century were nuts about this stuff.  It tastes, obviously, of mushrooms, but with wonderful aromatic citrus and gingery top notes from the spices.  10/10, this stuff deserves to make a comeback.