Place chicken breast in a saucepan, cover with cold water by 2 inches, bring to a boil over medium-high heat, then reduce to a low simmer and cook for 15 to 18 minutes until the internal temperature reads 165°F (74°C).

Remove the chicken, let it cool for 5 minutes, then shred into fine, thin strands about 1/4 inch wide using 2 forks.

In a large bowl, whisk together the 3/4 cup mayonnaise, 1 tsp celery salt, 1/2 tsp onion powder, 1/4 tsp garlic powder, 1/4 tsp black pepper, 1 tsp apple cider vinegar, and 1 tsp sugar until smooth and the sugar is dissolved.

Add the shredded chicken to the dressing and fold gently with a spatula until every strand is coated, about 1 to 2 minutes.

Cover and refrigerate for at least 30 minutes, then scoop generously onto a buttery croissant with a leaf of butter lettuce and serve with the filling piled high and visible.