In general, shiitakes come in two forms: the slender stemmed variety and the ones which are fatter, with thicker stems and caps. Mitsuwa and SF Supermarket sell the fatter variety, which have a meater flavor.
With so many on hand, they can be used liberally in pastas and soups, grilled, and sautéed with garlic and shallots.
But how to store the ones not eaten those first couple of days?
Everyone knows that mushrooms should only be stored in the refrigerator in paper bags because kept in plastic they quickly go bad. Use a brown paper bag--not a white one, which is coated with wax so the moisture stays inside the bag--in combination with paper towels. The moisture that normally accumulates on the outside of the mushroom is absorbed by the layers of paper.
Kept in the refrigerator another week or two, the brown paper bag-paper towel combination acts as a dehydrator pefectly drying the mushrooms. This technique only works successfully with shiitakes.
If by chance any of the dried shiitakes develop mold, discard and keep the good ones. In my experience, more than 95% will dehydrate without harm.