White balsamic vinegar has the same intense, sweet flavor as the more widely available dark brown balsamic vinegar. White balsamic vinegar, however, can be served with lighter-colored foods, such as mushrooms, without discoloring them.
Combine first 8 ingredients in a medium bowl; stir well with a whisk. Add mushrooms; toss well. Cover and marinate at room temperature at least 1 hour or up to 4 hours. Serve at room temperature with a slotted spoon.