Rotisserie Chicken Panini

In a small bowl, combine the first six ingredients; spread half over two bread slices. Layer with chicken, bacon, mozzarella cheese, onion and tomato. Spread remaining mayonnaise mixture over remaining bread slices; place over top. Brush outsides of sandwiches with butter., Cook on a panini maker or indoor grill until bread is browned and cheese is melted, 3-4 minutes.