Dehydrated Mushrooms

I bought mushrooms for the duck and bean soup that I wanted to make.  (Not worth a post; just leftover scraps in the fridge and navy beans.)  Then the soup kept getting pushed farther down the calendar as other ingredients got close to spoiling.  I had to come up with some way to preserve the mushrooms before they spoiled.

My research found two ways to salvage mushrooms without a pressure canner.  The first is freezing, after either steaming or sautéing.  The only problem I found with that for my current purpose was not knowing exactly how I wanted them seasoned for the soup.  The other preserving method was oven-drying, which I've done before.  (See oven-dried tomatoes and granola)  The principle behind that is slow-cooking, almost like smoking, to remove the moisture and give a roasted flavor.  Varieties of mushrooms prepared like this go at the market for a pretty penny, but you use less of them at a time to give umami flavoring to dishes.

I'm following the temperature and time settings from a post on The Spruce Eats.  The directions are simple and it works with any variety of mushroom.

1.  Wash mushrooms and remove dirt with a mushroom brush or towel.  Since you're dehydrating them, it really doesn't matter if they soak up a little water.

2.  Trimming stems is up to you.  I took off the harder portions and put them in the broth bag, leaving about 1/2" on each piece.  Slice caps 1/8" to 1/4" thick.  You don't need a ruler, just make them all the same thickness so they dry in the same amount of time.

3.  Place slices on a clean dishtowel.  Roll up like you are making a jelly roll, minus the powdered sugar.  Press out as much water as you can, so the oven doesn't have to do as much work.

4.  Preheat oven to 150ºF.  A convection fan is a bonus.  Arrange slices on a baking sheet and cook for 1 hour.  Flip slices and put them back in for another hour.  If not completely dried, turn over again and roast in 30 minute increments.  The humidity that day, variety of mushroom, and how well you squeezed out the water in the towel will determine how long the process takes.  When done, the pieces should feel dry, not rubbery.  They will also be very small.  Mushrooms are mostly water, and you just took out most of it.

5.  Cool slices completely, then store in a sealed container away from light.  Theoretically they last a year, but I would check on them at least once a month.

6.  To use, place in a heat-proof bowl and cover with boiling water.  Let sit for 20 minutes to hydrate. Remaining water can be used as an umami broth.  For use in soups, just toss in a handful and allow to simmer with the stock at least half an hour.

Difficulty rating  π