Sauté leek and garlic in butter in large skillet over medium heat about 8 minutes or until leek is tender. Stir in mushrooms, parsley and thyme. Sauté about 10 minutes or until mushrooms give off their juices. Stir in wine, sherry, pepper and salt. Cook, stirring occasionally, about 10 minutes or until liquid is reduced and thickened. Remove from heat; cool slightly. Transfer to work bowl of food processor or blender; process until smooth. Pour mixture into 3-cup tureen or bowl. Cover and refrigerate several hours or overnight. Garnish with fresh herbs. Serve with toasted French bread slices.