Preheat your oven to 350°F (175°C). Spray a 9x13 baking dish with nonstick spray.

Whisk together the eggs and chicken stock in a medium bowl and set aside.

Heat 1 tablespoon of olive oil in a large skillet, add the ground chorizo, and cook until browned for about 5-7 minutes. Transfer to a plate.

In the same skillet, add the remaining olive oil then sauté chopped onion, garlic, and celery for 5-6 minutes.

Add the chopped Calabrian chiles and butter to the skillet, allowing the butter to melt.

Remove from heat, stir in reserved chorizo and parsley, season with salt and pepper.

In a large bowl, combine the chorizo mixture with day-old bread cubes and toss gently.

Fold the egg mixture into the bread and chorizo blend until well coated.

Transfer the mixture into the baking dish, cover with foil, and bake for 30 minutes.

Remove the foil, increase oven temperature to 425°F (220°C), and bake for an additional 20 minutes.

Let the stuffing rest for 10 minutes before serving. Garnish with parsley if desired.