Remove the skin from the rotisserie chicken, then pull the meat from the bones and hand-shred into bite-sized pieces. Transfer to a large bowl.

Finely dice the onion and thinly slice the celery. Place them on a paper towel, lightly sprinkle with salt, and let sit for a few minutes. Pat dry.

Chop the parsley.

Halve or quarter the grapes, depending on their size.

Toast the pecans in a dry skillet over medium heat for 3–5 minutes, stirring frequently, until fragrant and lightly browned. Watch them closely as nuts can go from toasted to burned quickly. Remove from the heat, let cool, then roughly chop.

In a small bowl, whisk together 3/4 cup mayonnaise, 2 tablespoons lemon juice, 1/2 tablespoon Dijon mustard, 1/8 teaspoon garlic powder, and a pinch of salt and black pepper until smooth. Taste and adjust seasoning as needed.

Add 1/8 cup finely diced onion, 3 ribs of thinly sliced celery, and 1/4 cup chopped parsley to the chicken. Pour the dressing over the top and gently fold to combine.

Add 3/4 cup of grapes and fold in gently to avoid crushing.

Cover and refrigerate for at least 30 minutes to 1 hour.

Just before serving, stir in the chopped pecans. Taste once more and adjust seasoning if needed. Serve as desired and garnish if using.