Clean the chicken well. Remove the backbone and flatten the chicken with the palm of your hand, breaking the backbone.
Make the poaching sauce.
Crush the garlic cloves and the cinnamon stick. Thinly slice the ginger. Cut the scallions into 3” pieces and crush them.
Heat the oil in a large pot or Dutch oven until shimmering. Add the garlic, star anise, ginger, red onion and cinnamon stick. Saute for a minute or so until they become release their oils and you smell them. Add the chopped scallions, the Dr. Pepper, Tamari sauce, water, and honey. Simmer for 15 minutes. Stir in the sherry.
Cook the Chicken
Place the chicken, breast-side up in the poaching liquid. Bring to a simmer and cover. Simmer for 10 minutes then turn the chicken over so the breast meat is down and continue to simmer, covered, for another 10 minutes. Leave the pan covered and turn off the heat. Leave the chicken in the hot poaching liquid for another 30 minutes. The meat should register 165 on an instant-read thermometer when done.
Carefully remove the chicken to a cutting board and cover with foil.
Boil the poaching liquid for 10-15 minutes until slightly reduced and thickened.
Slice the chicken and serve with the poaching sauce and slice scallions.
Recipe Notes
Note: chicken can be stored in the poaching liquid, tightly covered for 5 days in the refrigerator.