Preheat the oven to 375 degrees F and butter a 3-quart baking dish. Melt 2 tablespoons butter in a large skillet over medium heat. Add the pancetta and cook, stirring, until browned, about 6 minutes. Remove with a slotted spoon and transfer to a plate.
Melt the remaining 6 tablespoons butter in the skillet, then add the onion, celery, sun-dried tomatoes, sage, thyme, 1 teaspoon salt and a few grinds of pepper. Cook, stirring, until the vegetables are tender, about 5 minutes. Add the broth and bring to a boil, then remove from the heat.
Whisk the eggs and parsley in a large bowl. Add the focaccia, ciabatta, pancetta, vegetable-broth mixture and fontina; stir until combined. Transfer to the prepared baking dish. Drizzle with the turkey drippings (or dot with butter); sprinkle with the parmesan.
Cover the dish with foil and bake 30 minutes, then uncover and bake until golden, about 30 more minutes.
You can assemble this stuffing the day before - keep in the fridge until baking.