Preheat the oven to 375F. Lightly grease a 9x13 baking dish.
In a large sauté pan, heat the oil over medium-high heat until hot, and add the sausage, using a spoon to crumble the sausage as it cooks.
1 Tablespoon canola oil, 1 pound mild Italian sausage, casing removed
Once the sausage begins to brown, add the butter, celery, onion, apple, sage, and rosemary. Stir to combine and continue to cook until vegetables are soft and sausage is fully cooked, about 5 minutes. Season to taste with salt and pepper.
2 Tablespoons unsalted butter, 2 ribs celery, diced, 1 medium onion, diced, 2 Granny Smith apples, cored and diced, 1 teaspoon dried sage, 1 teaspoon dried rosemary, Kosher salt & black pepper to taste
Remove from the heat and stir in the broth and beaten egg. Add the packaged stuffing mix and stir to combine.
1 ½ cups chicken stock, 1 large egg, beaten, 3 cups packaged stuffing mix
Pour the stuffing into the prepared baking dish and cover with foil. Bake covered for 15 minutes, remove the foil, and back for an additional 15-20 minutes or until cooked through and golden brown on top.