In a small slow cooker, add chicken and broth. Cook for 2 hours on high, then shred meat. Discard liquid. Alternately simmer chicken and broth in a saucepan until chicken is heated through and no longer pink. Season shredded meat with salt, 1/4 tsp pepper and 1/4 tsp celery seed. Toss with buffalo sauce until meat is evenly coated. Set aside.
Preheat oven to 375°F.
In a large saucepan bring water to a boil, add 12-15 jumbo shells. Cook for 9 minutes. Drain and let cool on a baking sheet or nonstick surface.
In a small skillet over medium heat, add chopped onion, celery and butter (or olive oil). Cook until tender and onions are translucent. Transfer to a small bowl.
In a large bowl, mix ricotta cheese, parmesan, egg, 1/8 tsp pepper, 1/8 tsp celery seed, blue cheese crumbles and vegetables. Add chicken mixture and stir well.
Prepare a small baking dish with a light coating of olive oil and a few spoonfuls of buffalo sauce. Fill one shell at a time with spoonfuls of chicken and cheese mixture. Carefully arrange in prepared baking dish. Drizzle with spoonfuls of buffalo sauce and sprinkle with shredded mozzarella cheese. Bake for 20-25 minutes. Serve warm.