Prepare pasta shells as directed on the package but cook al dente - about 10 to 12 minutes. Drain and put in cold water until ready to stuff.
Melt 3 tablespoons of butter in frying pan over medium heat. Add chicken pieces, celery and garlic. Fry until chicken is done and celery is crisp.
Put 1/2 cup hot sauce in a separate medium sauce pan. Add 1/2 cup mozzarella, 1/2 cup cheddar, 1/4 cup Parmesan, 1/2 cup sour cream, 8 ounces of cream cheese and 1/2 cup blue cheese salad dressing. Combine and stir over medium heat until all cheese is melted well blended. Remove from heat. Take 1/2 cup of the mixture and set aside.
Add chicken and celery to sauce pan and fold in. The goal is to have firm chicken pieces in each pasta shell.
Stuff each shell with filling. Place in a 9 x 13 casserole dish that has been sprayed with vegetable spray. Once bottom is covered, place any remaining shells on top.
In the same sauce pan used for stuffing, combine soup and 1/2 cup of water and 1/2 cup of the hot cheese mixture over medium heat. Once combined and heated, pour over the shells. Layer 1/4 cup of shredded cheddar on top.
Bake uncovered in a 350 degree oven for 20 minutes.