1 Skillet, 1 Small skillet, 1 Bowl, 1 Cutting board, 1 Large knife, 1 Small knife, 1 Tablespoon, 1 Wooden spoon, 1 Lid
1 Rinse chicken breasts and pat dry. Season with salt and pepper.
2 Heat oil in a pan and cook until chicken is browned, about 3 minutes on each side. Add enough water to cover bottom of pan, then cover with lid and cook until chicken is cooked through, about 4 minutes more. Remove from heat and let chicken cool.
3 Coarsely chop the walnuts and toast in a dry skillet.
4 Rinse grapes, drain and cut in half.
5 Rinse celery, pat dry, remove any strings and finely chop celery.
6 Rinse scallions, pat dry and finely chop.
7 Cut the chicken into strips.
8 Mix all the prepared ingredients in a bowl with the sour cream, yogurt and tarragon.
9 Season with salt, pepper and Worcestershire sauce. Let stand for 30 minutes.
10 Rinse endive, shake dry and cut out the core, then cut crosswise into thin strips and add to chicken mixture. Toast bread under a preheated broiler, watching carefully, or in a toaster oven. Divide chicken salad among toasts and serve.