1Heat oven to 350°. Remove stems from mushroom caps; reserve caps. Finely chop enough stems to measure about 1/2 cup. Discard remaining stems.
2Mix chopped mushroom stems and remaining ingredients in small bowl until well blended. Spoon into mushroom caps, mounding slightly. Place in ungreased jelly roll pan, 15 1/2x10 1/2x1 inch.
3Bake 15 to 20 minutes or until thoroughly heated. Serve warm.