Allow the toasted bread to sit approximately 24 hours, until hard.
Preheat oven to 165 degrees C (325 degrees F ). Lightly grease a 22x33 cm baking dish.
Melt the butter in a medium saucepan over medium heat. Stir in the onion and celery and slowly cook until soft. Remove from heat and drain.
Crush the bread into crumbs with a rolling pin. Place the crumbs in a large bowl. Mix the eggs and chicken broth into the bread crumbs. The mixture should be moist, but not mushy. Use water, if necessary, to attain desired consistency. Mix in the onion, celery, sage, garlic powder, salt and pepper.
Press the mixture into the baking dish. Bake 1 hour in the preheated oven, or until the top is brown and crisp.