Dice the cooked chicken into ½-inch cubes and set aside. Dice the celery, halve the grapes lengthwise, finely slice the scallions, chop the toasted pecans, and mince the fresh dill—this prep work ensures everything comes together smoothly. In a bowl, whisk together the mayonnaise, sour cream, Dijon mustard, salt, and pepper until smooth. Squeeze the fresh lemon juice directly into the dressing and stir to combine. The acidic lemon juice brightens the richness of the mayo and sour cream, creating a more balanced flavor.

In a large bowl, add the diced chicken, diced celery, halved grapes, sliced scallions, and chopped pecans. Pour the dressing from Step 1 over the chicken mixture and fold everything together gently until all ingredients are evenly coated. I like to use a rubber spatula rather than stirring vigorously, which helps keep the grapes and pecans intact while ensuring the dressing distributes throughout without breaking down the delicate chicken pieces.

Transfer the chicken salad to a covered container and refrigerate for at least 2-4 hours. This resting time allows the flavors to meld together and lets the celery soften slightly while maintaining its pleasant crunch. The cold temperature also helps the mayo-based dressing firm up, making the salad easier to pile onto the croissants without becoming too loose.

Slice each large croissant in half horizontally. Spoon a generous portion of the chilled chicken salad onto the bottom half of each croissant, then cap with the top half. Serve immediately while the croissants are still tender and the salad is pleasantly cold. For a more elegant presentation, I sometimes place a small lettuce leaf or herb sprig on the croissant before adding the chicken salad to add visual appeal and prevent the croissant from becoming too soggy.