For the sauce: Whisk together the ketchup and hot sauce in a small bowl and set aside.
For the meatloaf: Preheat the oven to 350 degrees F. Grease a 9-by-5-by-3-inch loaf pan with cooking spray and set aside.
Melt the butter in a medium saute pan over medium-high heat. Once melted, saute the celery and onion until softened, 3 to 5 minutes. Transfer the mixture, with the drippings, to a large bowl. Add the hot sauce to the bowl and stir to combine. Add the chicken, blue cheese, salt, pepper, eggs and 1 1/2 cups of the panko and mix until well combined.
Press the mixture into the prepared loaf pan, pressing more in the center of the loaf to create a divot. This will allow the meatloaf to bake evenly and not create a mound after it is baked. Spread the sauce over the top of the meatloaf. Mix the Parmesan with 1/2 cup of the panko and sprinkle the mixture on top of the sauce. Bake until the center is set and the top is golden brown, 45 minutes to an hour. Let rest about 15 minutes before cutting to serve.
Meanwhile, toast the remaining 1/4 cup panko in a dry pan until lightly golden and set aside.
Garnish the meatloaf slices with the toasted panko and chopped celery leaves.