Cube baguette and place in a baking dish or colander to dry out over night.
Grease a 9x13 baking dish and preheat the oven to 375°.
In a large skillet melt the butter. Add celery, onion, mushrooms, and garlic. Saute over medium heat for 10-15 minutes or until the onions go clear and the vegetables are tender. Season to taste with salt and pepper.
Place the bread cubes in a large bowl. Add the cooked vegetables, wine, broth, parsley, and tarragon. Adjust seasonings.
Spoon dressing into prepared baking dish. Bake for 30 minutes. Cook 15 minutes longer, depending on how crisp you like your dressing.
Nutritional values are approximate and are based on 1/6 of the recipe. Refrigerate leftovers promptly and use within 4 days.