1.Flatten Chicken To 1/4-In. Thickness; Sprinkle With Salt And Pepper. In A Large Skillet, Cook Chicken In 1 Tablespoon Oil For 5-10 Minutes On Each Side Or Until Juices Run Clear. 2.Meanwhile, For Pesto, Combine The Basil, Nuts, Garlic, Salt And Parmesan Cheese In A Blender Or Food Processor; Cover And Process Until Well Blended. While Processing, Gradually Add Remaining Oil In A Stream. Spoon Over Chicken. Top Each With A Slice Of Mozzarella. Sprinkle Mushrooms Around Chicken. Cover And Cook For 5 Minutes Or Until Cheese Is Melted And Mushrooms Are Tender.