Roast chestnuts, then peel and roughly chop. Optionally, they can be boiled or steamed. Use 1 tablespoon of butter to grease a 9x13 casserole dish.
In a large skillet, over medium heat, fry pork sausage along with chopped celery, onion, and carrot. After a few minutes, add 5 tablespoons of butter, apple, and chopped roasted chestnuts. Sauté until veggies are tender, fragrant, and the sausage is cooked through.
Season stuffing mixture with salt, black pepper, and crushed red pepper. Add chopped sage, parsley, rosemary, and thyme. Stir in chopped prunes (or cranberries) and remove from heat.
Mix the sautéed vegetable mixture with the bread cubes and add it to the casserole dish. In a large measuring cup, whisk together eggs, milk, chicken broth, and 2 tablespoons of melted butter. Pour over the bread mixture; stir until evenly moistened.
Bake stuffing, covered with foil, in a 350°F preheated oven for 20 minutes, then uncover and bake for another 10 minutes or until heated through and lightly crisped on top.
Notes
You can assemble this stuffing a day ahead, refrigerate it, then bake just before serving.
If you prefer stuffed turkey, stuff this chestnut dressing inside the bird instead of serving it as a side dish.
If substituting fresh herbs for dried, use 3 times as much.
Baking time may take longer because ovens vary. Make sure the stuffing is no longer jiggly in the center.