Step 1

Preheat the oven to 425 degrees F.

Step 2

Add the butter to the bottom of a large pot over medium heat. Add the onions and cook, stirring every so often, until the onions are caramelized and deep brown, about 20 minutes. Add the oregano, thyme, salt and pepper, then stir. Sprinkle over the flour and stir to coat the onions. Add the wine to deglaze, scraping the bottom of the pot. Bring to a simmer, then stir in the broth and chicken. Cook, stirring, until slightly thickened, about 3 minutes.

Step 3

Add half of the sauce to the bottom of a 9-by-13-inch baking dish. Add the cubed bread in a single layer, then top with the remaining sauce. Sprinkle over the Gruyère. Lightly cover the top of the casserole with foil and bake until bubbly, about 20 minutes. Remove the foil and bake until the cheese is browned, about 15 more minutes. Remove and let rest for 10 minutes before sprinkling over chopped parsley to serve.