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How exactly do you roast them, any idea?

They should do fine on maple. The key is getting it fresh so it has a high moisture content and isn't already populated with an aggressive native species

Fresh. Gotcha.

I just Googled "roasted shiitake mushrooms" and Martha Stewart's recipe came up. I had previously washed the mushrooms with water, so I had to leave them in longer, but otherwise it worked great.