Note: You need to prep this dish and let it sit covered in the fridge overnight - or up to 6 hours. This is a crucial step to ensure all flavors soak into the bread.
Brush a 9x13-inch glass baking dish with 1 Tbsp. olive oil. Set aside.
4 Tbsp. olive oil, divided
Heat 1 Tbsp. oil in large skillet over medium-high heat. Add the celery and onions; sprinkle with salt and pepper. Sauté until vegetables are soft, about 5-7 minutes. Scrape into very large bowl.
2 cups chopped celery (about 6 stalks), 1 large onion, diced (yellow, white or red)
Add 1 Tbsp. oil to same skillet. Add mushrooms; sprinkle with salt and pepper. Sauté until mushrooms brown and liquid evaporates, about 4-5 minutes. Scrape mushrooms into bowl with celery.
1 cup white mushrooms, sliced (about 4 oz.), 1 cup baby bella mushrooms, sliced (about 4 oz.)
Add remaining 1 Tbsp. oil and sausage to same skillet. Sauté until brown and cooked through, about 8 minutes; add to bowl with vegetables.
1 pound hot Italian sausage, ground (or mild if preferred)
Add the broth and brandy to the same skillet. Bring to simmer, scraping up browned bits.
1 cup vegetable broth (or chicken broth), 3 Tbsp. brandy, 1 Tbsp. fresh rosemary, chopped, 1 Tbsp. fresh sage, chopped, 1 Tbsp. fresh oregano, chopped, salt and pepper to taste
Pour broth mixture into same bowl. Add in the herbs, salt, and pepper and combine. Then mix in the bread.
1 pound (8 oz.) loaf country white bread with crust (day old or oven dried, see notes)
Spoon stuffing into prepared dish. Let cool for a bit if still warm before covering with plastic wrap. Refrigerate overnight or for at least 6 hours.
When ready to bake, preheat oven to 375°F. Remove plastic wrap; cover stuffing with foil. Bake 30 minutes. Uncover; bake until top begins to brown, about 25 minutes longer. Or if you don't have time to wait 25 minutes, broil and watch carefully so tops don't brown. Enjoy!