Put the chicken thighs, lemon, cilantro leaves and stems into a skillet or saucepan. Fill with water just to cover the chicken and season generously with salt and pepper. Bring to a boil over medium heat, then reduce the heat to maintain a very gentle simmer. Cook until the chicken is tender and falling from the bones, about 40 to 45 minutes.
Remove the chicken from the poaching liquid and allow to cool. When cool, remove the skin and strip the meat from the bones, discarding the skin and bones. Reserve the meat.
In a bowl, mix together the mayonnaise, curry, honey, and lemon juice. Stir in the scallions, celery, and grapes until combined. Add the cooled chicken meat and toss to combine. Season with salt and pepper, to taste.
Serve heaping portions of the salad in butter lettuce leaves.