Preheat oven to 350. Grease a 9x13 inch baking dish with butter.
Place the stuffing cubes in a large mixing bowl.
In a large saute 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. Don't wash the pan but scrape out every last bit of vegetables, otherwise they will burn in the next step.
In the same pan, cook the sausage over medium heat for 8 to 10 minutes, until browned and cooked through, breaking up the sausage with a metal spatula while cooking (the largest pieces should be no greater than 1/4 inch). 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 to 75 minutes, uncovered, until deeply golden and crisp on top.