Cut the tops off the bell peppers and remove the seeds and membranes. Place them upright in a baking dish.
In a large mixing bowl, combine shredded chicken, buffalo sauce, softened cream cheese, half of the shredded cheddar cheese, diced celery, garlic powder, onion powder, and a pinch of salt and pepper. Mix until well blended.
Fill each bell pepper with the buffalo chicken mixture, pressing down gently to pack it in.
Sprinkle the remaining cheddar cheese over the top of each stuffed pepper. Add blue cheese if using.
Cover the baking dish with aluminum foil and bake for 25 minutes.
Remove the foil and continue baking for an additional 10-15 minutes until the peppers are tender and the cheese is melted and slightly golden.
Let cool slightly before serving and garnish with freshly chopped parsley or sliced green onions.
Notes
Feel free to adjust the amount of buffalo sauce based on your heat preference.