Cut the drained, cooled, oven-poached chicken into bite-size chunks. Add a little celery, strings removed and finely diced, if you like, plus a little finely chopped red onion. Sprinkle with salt and pepper to taste and chopped fresh herbs—chives, tarragon (don’t overdo it), parsley, dill, or combinations of any of these are all very nice. Very gently toss the ingredients in a bowl with a rubber spatula just to combine.
In a small bowl, stir together equal parts reduced-calorie mayonnaise and low-fat plain yogurt; if you like, stir in a spoonful of coarse-grained or Dijon mustard to taste (use judiciously). Add just enough of this dressing mixture to moisten the chicken without making it too gooey—start with less; you can always add more.
Pile the chicken salad onto whole wheat bread, toasted or not. Top with ripe tomato slices, well salted, and a piece of romaine or red leaf lettuce. Top with another slice of whole wheat, cut in half, and dig in.