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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MUSHROOMS (au Beurre)
Trim the stems, and rub two pints of button mushrooms with flannel dipped in salt. Put them in a stewpan with three or four ounces of good butter, slightly browned, and stir them very gently, to get the butter well about them. Shake the pan over a moderate fire, that the mushrooms may not settle at the bottom. When they have well imbibed the butter, add a little pounded mace, salt, and cayenne, and cover closely by the side of the fire, to simmer until tender, when they will be found excellent without any other addition. Serve them hot on toast at breakfast or luncheon. If to be eaten cold, drain them from the butter, which may be used as a flavouring for other dishes, and put them in a cool place, to be served next day, but they will keep for several days. When mushrooms are plentiful, they may be kept thus prepared many weeks, in pots, with a little clarified butter run over the top to exclude the air. Warm up when required. Time, about twenty to twenty-five minutes altogether.
The hot dish at the centre of this entry is straightforward Victorian buttered mushrooms, but the recipe does not end there: it closes with instructions for holding cooked mushrooms for days in a larder and for weeks sealed under clarified butter. Those steps are the reason this page carries a warning, and they cannot be salvaged by adjusting a time or a temperature.
- Why the potting failsMushrooms are a low-acid food, and a pot sealed with a layer of clarified butter is precisely the oxygen-free environment in which Clostridium botulinum spores germinate and produce toxin. Nothing in the method reaches a spore-killing temperature, and "warm up when required" does not destroy the toxin once formed. Disregard the potting instructions entirely; for preserving mushrooms, use a current tested recipe.
- "A cool place, to be served next day"This assumes a stone larder and a household that ate what it cooked. Cooked mushrooms held at room temperature are a well-known vehicle for bacterial growth, and the original's confidence that "they will keep for several days" reflects pre-refrigeration practice, not food safety.
- Two pints of buttonsVictorian recipes commonly measure mushrooms by volume rather than weight. Two pints of small button mushrooms is roughly 1 lb, or about 450 g. They will collapse to a fraction of that volume in the pan.
- Cleaning without waterThe flannel dipped in salt is doing the work of a dry brush or a barely damp cloth. Mushrooms are largely water and take up more if soaked, which prevents them from browning and dilutes the butter they are meant to absorb.
- Butter quantityThree or four ounces (85-115 g) for a pound of mushrooms is deliberate excess: the surplus butter, drawn off later, was a prized flavouring in its own right, as the recipe notes. For a plain hot dish, half that is ample.
- Pounded maceMace is the dried outer covering of the nutmeg seed, warmer and less sweet than the nutmeg itself. Ground mace from a jar is the direct substitute; a quarter teaspoon suits this quantity.
- "A moderate fire" and "by the side of the fire"On a range this means medium heat for the initial toss, then the gentlest possible simmer with the lid on, which on a modern hob is the lowest setting. The twenty to twenty-five minutes given is total, and is longer than most cooks would now give button mushrooms; they are tender well before that and will be soft rather than firm at the end of it.
- YieldAbout 1 lb of mushrooms and the butter they carry will serve two generously on toast, or four as part of a larger breakfast.
Cassell's belongs to the era when buttered or potted mushrooms were a standard autumn item in an English kitchen, made when field mushrooms came in quantity from pasture and hedgerow. Potting -- cooking a food, packing it into an earthenware jar and sealing it with a layer of clarified butter -- was one of the great preserving techniques of the British larder, applied to shrimps, beef, tongue, cheese and game as readily as to mushrooms, and it worked well enough in a cold stone room to become traditional long before anyone understood what it was excluding and what it was encouraging. The same logic produced potted shrimps, which survive as a delicacy because they are now made and eaten quickly under refrigeration rather than kept for weeks. Serving the hot version on toast at breakfast or luncheon places the dish squarely in the Victorian savoury tradition, where a small buttery mushroom or kidney dish sat alongside the eggs and bacon.