MARINADE: Simmer vinegar, peppercorns and bay leaves in a small covered saucepan 10 minutes over medium-low heat. Bring to a boil over medium heat. In a large saucepan, combine water and salt; bring to a boil. Add mushrooms. Cover tightly and simmer over low heat 10 minutes. Strain mushrooms; discard cooking liquid. Let cool. Arrange equal amounts of mushrooms in pint canning jars. Pour boiling marinade over mushrooms to cover. Place lids on jars; seal tightly. Let cool to room temperature; refrigerate. Serve chilled.