Heat a pot of water over high heat until boiling.

Cook the chicken: When the water is hot, add the chicken and cook at a simmer for until the chicken has reached an internal temperature of 160°F (71℃). Remove from water and then dice into small pieces and transfer to the fridge to cool.

Prep the ingredients per the instructions above.

In a medium bowl, mix the minced onion, celery, and mayo, and reserve in the fridge.

Make the chicken salad: Once cooled, add the chicken to the mayo mixture. Season with salt and pepper to taste.

Layer the wrap with cheese, lettuce, tomato, and chicken salad. Fold in the ends and roll up tight.