1/2 cup shredded fresh mozzarella cheese (3 ounces)
1/2 cup shredded fontina cheese (4 ounces)
1/4 cup crumbled Gorgonzola cheese (1 ounce)
1/2 cup shredded provolone cheese (3 ounces)
4 ciabatta rolls, halved lengthwise, or 8 slices firm white sandwich bread
8 arugula leaves
In a small bowl, combine the cheeses. Spread the cheese on the bottoms of the ciabatta rolls, top with 2 arugula leaves and close the panini.
Set a large cast-iron skillet or griddle over moderately high heat. Arrange the panini in the skillet and weight them down with a smaller pan. Cook the panini until the outside is crisp and the cheese is melted, 3 minutes per side. Cut the panini in half and serve at once.