Step 1

Choose a heavy pot or Dutch oven with a tightfitting lid. It should be large enough to hold the chicken snugly, but not much bigger. Fill pot about 2/3 full with cold water, but don’t put the chicken in yet. Boil some extra water in a teakettle.

Step 2

Add scallions and peppercorns to water, cover and bring to a rolling boil. Turn off heat and slip chicken pieces into the hot water. If needed, add boiling water from the kettle to cover chicken with water by 2 inches. Replace the lid and let chicken rest in the hot water for about 2 hours. Do not turn the flame back on: The pot will retain enough heat to cook chicken thoroughly and safely. (To test, cut into 1 piece of chicken and check the meat near the bone. If it is still pink, return the pot to low heat, bring the water to a simmer and simmer 10 minutes more.)

Step 3

Lift chicken out of the pot. Remove and discard bones, skin and fat. Pat the meat dry with paper towels, then cut or shred into small bite-size pieces and transfer to a bowl. (Meanwhile, simmer cooking liquid until tasty, strain and refrigerate or freeze to use as chicken stock.)

Step 4

In a bowl, whisk together juice of 1/2 lemon, mayonnaise and sour cream. If using, whisk in mustard or brine. Taste and adjust the seasonings and thickness to your liking. Pour over chicken, scraping the bowl clean with a rubber spatula.

Step 5

Add celery, onion if using, nuts, herbs and salt and pepper. Toss gently but thoroughly. Refrigerate, covered, at least 4 hours. Taste and add salt and pepper as needed. Sprinkle with herbs before serving.