Serve these mushrooms with a loaf of rustic bread and a soft, creamy cheese, like an herb-coated Camembert.
Using a damp towel, gently wipe dirt from mushrooms. Trim the stems flush with the caps; discard stems.
Place mushrooms in a medium bowl, and add the remaining ingredients. Toss to combine. Set mushrooms aside at room temperature, stirring occasionally, to marinate, at least 20 minutes or up to 4 hours. Serve at room temperature.