Divide chicken and cheese evenly between 2 bread slices. Top with remaining bread slices.
Coat tops of sandwiches with cooking spray. Place sandwiches, coated sides down, in a grill pan or large nonstick skillet over medium heat. Coat tops of sandwiches with cooking spray. Place a piece of foil over sandwiches in pan; place a heavy skillet on top of foil to press sandwiches. Cook 3 minutes or until lightly browned. Turn sandwiches over; replace foil and heavy skillet. Cook 2 minutes or until lightly browned. Cut sandwiches in half, and serve immediately.
Note: We used a smaller skillet weighted with 2 canned goods to press the sandwiches, but a cast-iron skillet would also do the trick.