Prepare the following, adding each to the same medium bowl as you complete it: Dice 1 large celery stalk (about ½ cup). Finely dice ½ medium red onion or thinly slice 3 medium scallions (about ½ cup). Quarter ½ cup red grapes if desired. Juice ½ medium lemon until you have 1 tablespoon. Pick the fronds from 4 fresh dill sprigs and coarsely chop (about ¼ cup).
Add 1 pound shredded cooked chicken, ¾ cup mayonnaise or ½ cup plain Greek yogurt plus ¼ cup mayonnaise, 1 ½ teaspoons Dijon mustard, and ½ teaspoon celery seeds if desired. Stir until evenly combined. Taste and season with kosher salt and black pepper as needed.
