Simmer raisins in water in a small saucepan for 1 minute just to plump them. Set aside.
Sauté celery and onion in butter until soft in a large skillet. Stir in chicken broth, salt, sage, and pepper.
Put bread cubes and walnuts into a large bowl. Stir in celery mixture, and then raisins with their soaking water. Toss gently until evenly moist.
Makes approximately 10 cups.