Parmesan-Crusted Chicken with Watercress Salad

1 T whole grain mustard
1 egg white
1 c whole wheat bread crumbs
1/3 c grated Parmesan cheese
1 tsp lemon zest
4 chicken breasts (pound to 1/2 thickness)
1/4 chopped basil
1 T balsamic vinegar
2 tsp olive oil
1/8 tsp salt
2 bunches watercress, arugula or mixture of both
3 c grape tomatoes, quartered
1/2 red onion sliced

Preheat broiler. Combine mustard and egg white in shallow bowl. Combine bread crumbs, cheese and lemon zest in another bowl. Coat chicken with mustard mixture and then dip into bread crumb mixture, pressing to coat thoroughly with crumbs. Place on prepared rack. Broil 10 minutes, turning once or until chicken is golden brown and thermometer inserted into thickest portion registers 160 F and juices run clear. Whisk basil, vinegar, oil and salt in medium bowl. Add watercress, tomatoes and onion, and toss to coat well. Divide salad evenly among 4 plates and top each with 1 sliced chicken breast. Garnish with shaved Parmesan, if desired.