Preheat the oven to 350°F. Grease a 9 x 13-inch baking dish with butter.
Place the stuffing cubes in a large mixing bowl.
In a large sauté pan, melt the butter. Add the onions and celery and cook over medium heat, stirring occasionally, for about 8 minutes, or until the vegetables are soft. Add the garlic and cook 2 minutes more. Add the vegetables to the stuffing cubes.
In the same pan, cook the sausage over medium heat for 8-10 minutes, until browned and cooked through, breaking up the sausage with a metal spatula while cooking. Add the browned sausage and fat to the bread cubes and vegetables.
Add the chicken broth, egg, rosemary, sage, parsley, salt and pepper to the bread cube mixture and mix until the bread is soft and moistened. Transfer the stuffing to the prepared baking dish and bake for 65-75 minutes, uncovered, until deeply golden and crisp on top.
