Preheat the oven to 425°F. Spray a rimmed baking sheet (12"x17" cookie sheet) with nonstick cooking spray. You will need two of these baking sheets.
In a large mixing bowl, add the shredded chicken, softened cream cheese, buffalo sauce, garlic powder, onion powder, kosher salt and black pepper. Stir until everything is evenly combined.
3 cups shredded or cubed cooked chicken, 4 ounces cream cheese, ½ cup buffalo sauce, 1 teaspoon garlic powder, 1 teaspoon onion powder, ½ teaspoon kosher salt, ¼ teaspoon ground black pepper
Arrange 6 large flour tortillas onto the prepared baking sheet, so they slightly overlap and hang over the edges, creating a base layer.
8 large burrito-sized flour tortillas
Sprinkle half of the shredded mozzarella cheese evenly over the tortillas. Then spread the buffalo chicken mixture evenly over top the shredded cheese. Sprinkle the remaining shredded mozzarella cheese over top the buffalo chicken layer.
3 cups shredded mozzarella cheese
Place the 2 remaining large flour tortillas in the middle of the sheet pan on top of the cheese. Then fold the overhanging bottom tortillas up and over the top layer (they should meet the two large flour tortillas that were placed in the center).*If needed, use toothpicks to connect the tortillas together so they stay while baking. But once you put the baking sheet on top of it, that holds the tortillas together really well. So you shouldn't need toothpicks. Brush the top of the flour tortillas with the melted butter.
2 tablespoons butter
Spray the flat bottom underside of a second sheet pan that's the same size as the first one. Firmly press the flat bottom of the sheet pan over top the quesadilla. Press it down to weigh down the quesadilla.
Bake for 20 minutes. Then carefully remove the top sheet pan and continue baking for 5-8 more minutes until the tortillas are golden brown and the cheese is fully melted.
Remove from the oven and let it rest for about 5 minutes.
Drizzle with the blue cheese dressing and buffalo sauce (optional if using) and sprinkle the green onions on top. Cut into squares and serve warm. Enjoy!*Instead of drizzling, you can also serve the sauce on the side for people to dip the quesadillas into bleu cheese dressing OR ranch dressing, buffalo sauce, sliced green onions