Melt butter in skillet; saute onion and celery, until tender (about 15 minutes on low). In a large mixing bowl, combine crumbled corn bread, white bread, onions, celery, sage and black pepper. Pour about 2 cups hot broth over the mixture and blend well, but do not beat. Stir in eggs. Mixture should be soft, but still hold its shape. Add more broth if too stiff, and taste for seasonings.