Preheat the oven to 400°
On a baking sheet, toss the bread with 1/2 cup of the olive oil. Spread the bread in a single layer and toast in the oven for 15 minutes, stirring once, until golden brown.
In a skillet, toast the fennel seeds over moderate heat until fragrant , about 2 minutes. Transfer to a mortar or spice grinder; coarsely grind.
In a large skillet, heat 2 tablespoons of olive oil. Add the pancetta and cook over high heat, stirring, until crisp, about 3 minutes.
Add the rosemary and chile and cook for 1 minute.
Add the onion, fennel, fennel seeds and thyme and season with salt and pepper. Cook, stirring, until the vegetables are lightly caramelized, about 8 minutes.
Discard the rosemary and chile. Stir in the lemon zest and add to the croutons.
Place the skillet over high heat. Add the wine and bring to a boil, scraping up the browned bits. Boil until reduced to 1/3 cup, about 4 minutes.
Add the chicken stock and bring to a boil. Pour the hot stock mixture over the croutons and toss well.
Wipe out the skillet. Add 3 tablespoons of the butter and the chestnuts and cook over moderately high heat, stirring, until lightly browned, about 5 minutes.
Add the chestnuts to the stuffing, season with salt and pepper and let cool completely. Add the eggs and parsley and toss well.
Transfer the stuffing to a 9-by-13-inch baking dish. Cover with foil and bake for 30 minutes.
Remove the foil and dot the stuffing 3 tablespoons of butter. Bake for about 20 minutes, or until crisp on top.
Serve hot.