Step 1

Preheat the oven to 375 degrees F. Butter a 9-by-13-inch baking dish.

Step 2

Heat the oil in a large skillet over medium heat. Add the sausage and cook, stirring occasionally with a wooden spoon and breaking up any clumps, until browned, about 5 minutes. Transfer the sausage with a slotted spoon to a large bowl.

Step 3

Add the wine to the skillet and cook until almost all the liquid has evaporated, scraping up any browned bits, about 2 minutes. Add 1 tablespoon of the butter to the skillet, and then add the mushrooms. Season with 1 teaspoon salt and some pepper. Cook, stirring occasionally, until the mushrooms brown and have cooked down to about half their original volume, about 5 minutes. Transfer the mushrooms with a slotted spoon to the bowl with the sausage.

Step 4

Melt the remaining 7 tablespoons butter in the skillet. Then add the celery, onions, sage and thyme and cook until softened, about 5 minutes. Add the broth and bring to a simmer.

Step 5

Beat the eggs and parsley in another large bowl. Add the bread cubes and toss. Add the reserved sausage and mushrooms and toss together. Pour in the vegetables and broth and toss again until evenly coated. Transfer the mixture to the prepared baking dish and cover with foil. Bake for 30 minutes. Then uncover and continue to bake until golden, about 30 minutes more. Garnish with celery leaves if using.