2 c. cider vinegar
2 c. wine vinegar
2 c. water
1 slice gingerroot
2/3 nutmeg, grated
1/2 tsp mace (ground)
1/2 tsp cinnamon
6-10 cloves garlic, minced
1/2 tsp salt
1/2 a small long pepper
1/4 tsp ground pepper
4 threads saffron
Mix vinegars, water, and spickes in a large, non-reactive pot. Add mushrooms until mushrooms reach above liquid line. Heat at medium-high until simmering. Cover and simmer for 10 minutes. Using a slotted spoon, remove mushrooms from brine and pack into a jar or crock. Pour in brine mixture to cover.
Researches into volumes like Fast and Feast period cookbooks (like Take a Thousand Eggs and Pleyn Delit) and resources on spices have convinced me that medieval cooks worked saffron, nutmeg, mace and cinnamon into everything they could. Gingerroot and pepper seem to be added to dishes where piquancy was required; cubebs were mixed in with vinegar to form a marinade for the Polish court (Dembinska, p 166). I used a 1756 recipe in Putting Food by as my starting point for a spices list, but the spices are consistent with period spicing practice.
The spices are also similar to the the list of ingredients called for
in a recipe for "Pickled Champignons" from The Closet of the eminently
learned Sir Kenelme Digbie Kt. Opened (1671):
Pickled mushrooms were described by Apicus in Roman times. We know that pickled vegetables and side-dishes of cooked mushrooms appeared on medieval Polish and Russian tables (as documented in Food and Drink in Medieval Poland, in The Domostroi, in Bread and Salt, and in Old Polish Traditions). Domostroi, Bread and Salt, and Old Polish Traditions specifically mention preserving mushrooms by pickling. I chose to use half cider and half wine vinegar, but I cannot document that choice for period.
Putting Food By, by Ruth Hertzberg. (Brattleboro, Vt. : Stephen Greene
(for Circa 1756 recipe for pickled mushrooms)
Fast and Feast: food in medieval society by Bridget Ann Henisch. (University Park : Pennsylvania State University Press, 1976)
Forme of Cury, online version: http://www.pbm.com/~lindahl/foc/
The Lore of Spices: Their history and uses around the world, by J.O. Swann (NY: Cresent Books, 1991)
The Art of Cooking, by Apicus (sorry, I don't know which edition)
Food and Drink in Medieval Poland: Rediscovering a Cuisine of the Past. Maria Dembinska, revised and adapted by William Woys Weaver. (Philadelphia: University of Pennsylvania, 1999).
The Domostroi: Rules for Russian Households in the time of Ivan the Terrible. Edited and translated by Carolyn Johnston Pouncy. (Ithaca, NY: Cornell University Press, 1994)
Bread and Salt: A social and economic history of food and drink in Russia. R.E.F. Smith and David Christian. (NY: Cambridge University Press, 1984).
Old Polish Traditions: in the Kitchen and at the Table. Maria Lemnis and Henryk Vitry. (NY: Hippocrene, 1996).