Preheat oven to 400 degrees Fahrenheit.
Pre-bake flatbreads for 2 minutes. While the flatbreads are baking combine the shredded chicken, 1 tablespoon diced green onions, 1/4 cup buffalo sauce and minced celery stalk. Mix until well combined.
Remove the flatbreads from the oven, divide the whipped cream cheese among the four flatbreads and smear on each flatbread. Divide the buffalo chicken mixture, shredded cheddar cheese, and bleu cheese among the four flatbreads evenly. Bake the flatbreads for 5 minutes or until golden brown in color.
While the flatbreads are baking combine the Stonyfield Plain Greek Yogurt with 1 tablespoon of buffalo sauce. Set to the side once combined.
Remove the flatbreads from the oven, cut the flatbreads, sprinkle the remaining green onions on top of the flatbread. Place the greek yogurt buffalo sauce in a baggy, cut the tip off one of the corners of the baggy and pipe the sauce on top of the flatbread. Serve immediately.