Important: Safety Warning
This page describes home-canning methods from before the causes of botulism were understood. Canning low-acid foods without a pressure canner, as described here, can allow the growth of Clostridium botulinum, whose toxin is among the deadliest known. Follow current USDA home-canning guidelines instead.
This information has been left in for historical purposes but should not be acted upon.
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Potted Mushrooms
Large button mushrooms without any brown color inside them should be used, and about two quarts will be enough. Peel and remove the fur from the larger ones, put them all into a saucepan with one-half dram of powdered mace, two drams of white pepper and eight powdered cloves; place the pan over the fire and shake and toss it until the liquor from the mushrooms has all dried up. Then add two ounces of butter and cook until the mushrooms are well done; drain off the butter and leave until quite cold. Pack the mushrooms closely in an earthenware pot, pour over some warmed butter, cover with white paper, over this pour clarified beef suet to exclude the air, and set away in a cool place until wanted.
This is a nineteenth-century potting recipe: cooked mushrooms sealed under fat and stored at cellar temperature. The technique is the problem, and no adjustment of seasoning or timing fixes it.
- Why it fails: anaerobic storage of a low-acid foodMushrooms have a pH well above 4.6 and carry soil-borne Clostridium botulinum spores. Sealing them under butter and suet creates exactly the oxygen-free environment those spores need to germinate and produce botulinum toxin, which is odorless, tasteless and not destroyed by the gentle warming a potted preserve receives.
- "A cool place" is not a temperatureAn unrefrigerated larder or cellar can easily sit at or above the temperature at which Clostridium botulinum will grow. The recipe gives no acidification, no measured salt, no pressure processing and no holding temperature, so there is nothing in it that controls the hazard.
- The butter and suet are the seal, not a preservativeClarified fat excludes air and slows surface mold and rancidity, which is what the method was for. It does nothing against anaerobic bacteria, and by keeping oxygen out it actively favors them.
- Storage time is open-ended"Set away in a cool place until wanted" implies weeks or months. Toxin production needs only days under the right conditions, and a jar showing no swelling, smell or off appearance can still be dangerous.
- If you want potted mushroomsUse a current recipe intended for refrigerated short-term storage, or a tested pressure-canning procedure from a modern food-preservation authority. Do not adapt this one.
- On the units, for reading purposesA dram here is the apothecaries' weight, one-eighth of an ounce, about 3.9 g; half a dram of mace is roughly 1.9 g and two drams of white pepper about 7.8 g. Two quarts of button mushrooms is a volume measure, probably something over a pound once trimmed.
- "Remove the fur"This is usually taken to mean scraping out the gills of the larger, more open caps, which would darken the butter. On the face of it a cosmetic step, not a safety one.
Potting — cooking a meat, fish or vegetable down, packing it tight in an earthenware pot and sealing it under a cap of clarified fat — was one of the standard English methods of keeping food before mechanical refrigeration, and it survived into American hotel kitchens as a luxury item rather than a necessity. Oscar Tschirky, the Swiss-born maître d'hôtel whose name carried the Waldorf's reputation, put out The Cook Book by "Oscar" of the Waldorf in 1896, a vast compilation drawing on the English and French repertoires a grand hotel kitchen was expected to command. Potted mushrooms belonged to the cold larder alongside potted shrimps, tongue and game, meant for the sideboard, sandwiches or a savoury course. The insistence on pale button mushrooms "without any brown color inside" reflects the period's preoccupation with appearance in cold work, though traditional potting more usually relied on a seal of clarified butter alone.