Spanish serrano ham, like its more famous Italian cousin prosciutto, is salted and hung in drying halls to air-cure. It is made primarily in western Spain and is one of the country's classic tapas offerings. Traditionally cut thicker than prosciutto, serrano has a similar but more earthy flavor, in part derived from the sizable role acorns play in the pigs' diet. Although not as widely available as prosciutto, serrano ham is turning up more frequently in delicatessens and specialty-food stores. Steaming the mushrooms helps to rid them of excess moisture, creating a more concentrated mushroom flavor. Do not be surprised by how much they shrink, as they have a high moisture content.