In a large skillet over medium-high heat, soften the onion, celery and garlic in half of the butter. Add the meat and cook, breaking it up with a wooden spoon, until it starts to brown. Add the broth, wine and red pepper flakes. Simmer until the liquid has almost completely evaporated. Remove from the heat.
Add the fruitcake and bread. Season with salt and pepper and mix together. Transfer the mixture to a bowl, cover and refrigerate for 1 hour.
With the rack in the middle position, preheat the oven to 425°F (220°C).
Thoroughly pat the chicken dry with paper towel. Place the chicken, breast side up, in a baking dish. Season the inside and outside of the chicken with salt and pepper. Stuff the cavity of the chicken with the cooled pork mixture, pressing it in firmly. Depending on the size of the chicken’s cavity, there may be excess stuffing. In this case, cover the excess stuffing with foil before cooking. Tie the legs with butcher’s twine. With your fingers, spread the remaining butter over the chicken skin.
Roast for 15 minutes. Reduce the oven’s temperature to 375°F (190°C) and roast for 1 hour 10 minutes or until a thermometer inserted into the thigh, without touching the bone, reads 180°F (82°C).