This is part of any traditional antipasto plate or platter for Italians. Pickled vegetables like eggplant, mushroom, and even green tomatoes add a nice vinegary bite to all of the salty and fatty cheeses and meats.
Into a large pot, add water and vinegar. Bring it up to a boil and then add the salt. Add all the mushrooms and boil for 5 to 6 minutes.
Drain them and spread them out on a paper towel to cool and dry for about an hour.
Add the cooled and dried mushrooms to a large bowl, season with oregano, red pepper flakes, and garlic. Drizzle foil over the mushrooms and mix well.
Placed them into a 32 ounce mason jar and fill the jar with oil until it completely covers the mushrooms. Place the top on and refrigerate immediately.