Preheat the oven to 350 degrees F. Melt 4 tablespoons butter in a large deep skillet over medium heat. Add the bacon and cook, stirring, until browned, 10 to 12 minutes. Add the celery, onions, prunes, chestnuts, rosemary, 1 tablespoon salt and a few grinds of pepper. Cook, stirring occasionally, until the mixture softens and starts browning, 6 to 8 minutes. Stir in the chicken broth and bring to a simmer.
Combine the bread and broth mixture in a large bowl and gently mix until all the bread is moistened. Stir in the beaten eggs.
Butter a 3-quart baking dish. Add the stuffing and dot with the remaining 4 tablespoons butter. Cover with foil and bake 30 minutes. Uncover and continue to bake until golden brown, about 20 more minutes.