In A Bowl, Combine The First Eight Ingredients; Mix Well. Spoon Over Chicken. Grill, Uncovered, Over Medium Heat For 7 Minutes On Each Side Or Until Juices Run Clear. In A Large Skillet, Saute Onion And Garlic In Oil For 1 Minute. Stir In Mushrooms; Saute For 3-4 Minutes Or Until Tender. Add Spinach; Saute For 2 Minutes Or Until Wilted. Transfer To A Serving Platter; Top With Chicken.