Pre-heat the oven to 350°F.
Place the fruit-nut bread cubes evenly on a baking sheet. Melt 2 tablespoons butter and pour it over the cubes. Bake until lightly golden in color and slightly dried out, about 15-20 minutes.
In a large skillet, melt the remaining 2 tablespoons butter over medium heat, then add the fennel and onion. Cook for 8-10 minutes until softened and a bit caramelized. Transfer the mixture to a large bowl.
Add the toasted fruit and nut bread and stock to the bowl with the onion-fennel mixture and the stock. Mix to combine all ingredients (use your hands if you like — it’s fun!). The mixture should be moist but not soggy; add a little more stock if you like your stuffing wetter.
Season the stuffing with poultry seasoning, salt and pepper. Place in a 9-inch x13-inch buttered baking dish and bake for 30 minutes. (To keep the stuffing moist; cover the top loosely with foil while it bakes.)