This is a classic stuffing, but the method is key. You want bread cubes that hold their shape but are tender and moist all the way through, so stir everything together in a large bowl and then let the stuffing rest in the fridge overnight. This key step gives the cubes plenty of time to absorb all of the liquids and for the flavors to come together.
0 Spray a 9x13 baking dish (or any 3 quart casserole dish) with nonstick cooking spray.
1 Heat a large skillet over medium heat. Add butter and when butter is melted, add celery, onion, leeks, apple, sage, parsley, and 1/2 teaspoon salt. Cook, stirring frequently, until celery and onion are soft, 8 to 10 minutes.
2 Add sausage and cook, breaking it apart, until cooked all the way through, 8 to 10 minutes more.
3 Transfer sausage and vegetables to a large mixing bowl. Let cool slightly.
4 In a medium mixing bowl, whisk together eggs and 1/2 teaspoon salt until smooth. Slowly add in stock while whisking so that everything is evenly combined.
5 Pour stock mixture over sausage and vegetables. Add bread cubes on top.
6 Gently fold everything together until most of the stock mixture has been absorbed by the bread cubes (this may take a few minutes of stirring / folding).
7 Transfer stuffing to prepared baking dish. Cover tightly with foil.
8 Refrigerate overnight (or for about 8 hours).
9 When ready to bake, let stuffing come to room temperature.
10 Preheat oven to 350°F / 177°C.
11 Bake stuffing, covered, for 40 minutes. (Note: If the stuffing is cold when you transfer it to the oven, add 30 minutes to this initial bake time to insure it is cooked through.)
12 Remove foil and continue baking until stuffing is golden brown on top, about 30 minutes more.
