Preheat your oven to 350°F. Grease a 9x13-inch baking dish. If needed, cut day-old bread into 1-inch cubes.

In the same skillet, melt the butter. Add the diced onion and celery. Cook for about 8 minutes until soft. Stir in the minced garlic and cook for 2 more minutes.

In a large bowl, combine the bread cubes, cooked sausage, and sautéed vegetables. Stir in the chicken broth, beaten egg, poultry seasoning, chopped sage, parsley, salt, and pepper until the bread is evenly moistened. If needed, add a little bit more broth at a time until there are no dry spots.

Transfer the mixture to the prepared baking dish and bake uncovered for 45-55 minutes, or until the top is golden and crisp. Garnish with additional parsley.