Oven Prep: Preheat the oven to 350F and set a large baking sheet aside. Grease a 9×13” baking dish and set aside as well.
Toast the Bread: Cut the bread into 1” cubes and spread evenly across the baking sheet. Bake in the oven for 10 minutes, then carefully toss the cubes and spread out again. Bake again for an additional 5 to 15 minutes, until the bread is toasted and dry; this will vary based on the type of bread used and how packed the tray is. Set aside to let cool.
Aromatics: Melt the butter in a large sauté pan or pot over medium high heat. Add the celery and onion to the pot and sauté for 5 minutes, until beginning to brown.
Garlic & Spices: Add the garlic, sage, thyme, rosemary, parsley, black pepper, and nutritional yeast (if using) to the pan. Mix well, and sauté for another 1 to 2 minutes, to toast the spices. Turn the heat off and add in the toasted bread cubes and 1 1/2 cups of vegetable broth. Toss well; you want the cubes to be moist, but not soggy. Add additional broth as necessary.
Bake: Transfer to a baking dish and cover with foil. Bake covered for 15 minutes, then uncovered for 25-30 minutes, or until browned. If the stuffing is beginning to brown too much, loosely cover the top of it with foil again.
Serve: Remove from the oven and top with additional fresh parsley. Serve warm; stuffing is best served fresh, but leftovers will keep in the fridge for up to 5 days.