Preheat the Oven -Set the oven rack to the lower and upper-middle position. Preheat to 350ºF (177ºC).
Dry the Bread - Slice the bread into ¾" cubes and spread in a single layer on two large sheet pans. There should be about 16 cups. Toast in the oven until the edges are dry and crisp, about 10 minutes, gently stirring after 5 minutes. Allow them to cool completely on the sheet pan while cooking the rest of the stuffing.
Cook the Sausage - Heat a large skillet over medium heat. Add 1 tablespoon of butter. Once hot, add the sausage. Brown the surface and break it into smaller pieces. Cook until no longer pink, about 7 to 8 minutes. Transfer to a large bowl.
Saute Vegetables and Apples - Melt 2 tablespoons butter in the pan, then add onions, celery, and apples. Saute until tender, 7 to 8 minutes. Add garlic, and saute until fragrant, 30 seconds. Add sage, rosemary, thyme, salt, and pepper, stir and cook for 30 seconds. Transfer the mixture to the bowl with the sausage.
Soak the Bread - Stir in the cranberries and chopped walnuts. Stir in 12 cups of toasted bread cubes. There will be extra bread to use as desired.In a medium bowl or measuring cup, whisk together the eggs and chicken stock. Pour the liquid evenly over the bread and gently stir to combine. Soak for 5 minutes.
Prepare the Casserole - Grease a 9x13-inch baking dish with vegetable oil, softened butter, or cooking spray. Evenly spread the stuffing mixture into the dish. Sprinkle more cranberries, chopped walnuts, and herbs on top if desired.
Bake - Set the oven rack to the middle position. Cover with foil and bake for 20 minutes. Uncover and bake until the internal temperature reaches at least 144ºF (62ºC), about 10 to 15 minutes. Serve the stuffing warm.
Notes
Recipe Yield: 12 cups
Serving Size: 1 cup
Substituting Store-Bought Bread: Use 12 cups of dried bread cubes instead of fresh bread loaf.
Using Dried Herbs: Use half the amount of fresh herbs (sage, thyme, and rosemary), a total of 1 tablespoon dried. You can also use poultry seasonings or herbs de Provence, add 1 tablespoon.
Make-Ahead: Cut and dry bread up to 5 days before using. Store in an airtight container. Combine all of the stuffing ingredients, cover, refrigerate, and bake within 1 day. Bake covered for 30 minutes, then remove and bake until the internal temperature reaches at least 144ºF (62ºC) and the surface is dry.
Storing: Cool, cover, and refrigerate for up to 4 days. Freeze in a resealable plastic bag for up to 3 months.
Reheating: Cover individual portions on high power in the microwave in 30-second intervals until warm. Alternatively, heat in a 300ºF (149ºC) oven until warmed through.