1. Split each chicken breast in half lengthwise to form 2 cutlets. Heat a large skillet over medium-high heat. Coat the pan with cooking spray. Sprinkle chicken evenly with pepper. Add chicken to pan; cook 4 minutes on each side or until done. Remove chicken from pan. Wrap 1 prosciutto slice around each chicken cutlet.
2. Return pan to medium heat. Coat pan with cooking spray. Spread one side of each bread slice evenly with 1/2 teaspoon butter. Place 4 bread slices, buttered side down, in pan. Top each bread slice in pan with 2 tablespoons cheese; toast bread for 2 minutes or until underside is toasted and cheese melts. Remove the bread from pan. Recoat pan with cooking spray. Place the remaining 4 bread slices, buttered side down, in pan; toast 2 minutes or until toasted. Remove from pan.
3. Top each cheese-topped bread slice with 1 chicken cutlet. Spread 1 1/2 teaspoons mustard over untoasted side of each remaining bread slice. Combine arugula, shallots, and juice in a bowl; toss. Divide mixture evenly among sandwiches; top each sandwich with 1 bread slice, mustard side down. Serve with pear slices.
Beer Match: Try an amber ale like New Belgium Fat Tire ($1.50/bottle). The toasty malt and hoppy bitterness in these ales will complement the recipe's sweet pears and nutty cheese. --Gretchen Roberts