Sometimes, no matter how long you soak dehydrated mushrooms, and no matter how hot the water you use, they stay tough and chewy—it's like gnawing on a car tire, or a stale piece of jerky.
After rehydrating dried shiitakes in water for two hours, she takes them out of the liquid, removes the stems, and marinates the caps in a little oil and sugar for another hour before using them. (In terms of the temperature of the soaking liquid, Coombes doesn't specify—you can use hot water if you only have 10 or 20 minutes, but room temperature water will better preserve their flavor.)
And if you think that sounds like a long soak, Andrea Nguyenrecommends even more planning ahead: She removes the stems of the shiitakes first, then soaks the caps in water for 8 hours. "Follow this long soak method and the rehydrated mushrooms will be deeply flavored, amazingly firm and velvety when cut," she writes. "A long soak works wonders on cheapie dried shiitakes too!"
For plumper mushrooms with a better texture, marinate in a little oil and sugar for 1 hour before using.
Ping Coombes doesn't specify, but I'd recommend coating the mushrooms in oil (so that they're glistening and fully coated) and adding a pinch or two of sugar!
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