1 In a large resealable plastic bag, combine the oil, vinegar, garlic and thyme; add the mushrooms. Seal bag and turn to coat; refrigerate for up to 2 hours.2 In a small skillet, saute pears in oil and lemon juice until tender; cool slightly. Place in a small food processor; cover and process until blended.3 Stir in mayonnaise and walnuts. Cover and refrigerate until serving.4 Drain and discard marinade. Grill mushrooms in skillet, over medium heat, covered, for 3-4 minutes on each side or until tender.5 Top with onion and cheese slices. Cover and cook for 2-3 minutes or until cheese is melted.6 Serve on buns with arugula and mayonnaise mixture.

Source: Photo and Recipe Courtesy of Mushroom Council and Mushroominfo.com