Place chicken tenderloins in a large pot and cover with cold water or low-sodium chicken broth. Bring to a boil, then reduce to a low simmer, cover, and cook for 8–10 minutes until the internal temperature reaches 165°F.
Remove chicken from liquid and spread on a plate or cutting board. Allow to cool to room temperature (about 15 minutes) before proceeding.
Place cooled chicken in a deep bowl. Use a hand mixer on medium speed for 20–30 seconds until chicken is finely and evenly shredded. Do not over-mix.
Pulse celery in a food processor 5–6 times, or mince very finely with a knife. Pieces should be no larger than 1/8 inch.
Add Duke's mayo, minced celery, onion powder, garlic powder, salt, and pepper to the shredded chicken. Stir well to combine. Taste and adjust seasoning.
For best results, refrigerate for at least 30 minutes before serving. Serve on croissants, bread, or with crackers.