INGREDIENTS
1 1/2 lb
skinless, boneless chicken breast halves
1/4 cup
plus 2 tablespoons mayonnaise
2 tsp
Dijon mustard
Kosher salt and freshly ground pepper
1/4 cup
plus 1 tablespoon minced red onion
2
medium celery ribs
1 1/2 tbsp
minced flat-leaf parsley
3 cups
shredded iceberg lettuce
2
medium tomatoes, thinly sliced
12
slices grainy whole wheat bread, lightly toasted