Preheat oven to 350 degrees. Peel apart bread slices into small chunks. We didn't use the end slices. Place bread chunks on 2 separate shallow baking pans. Bake for 3 minutes, then swap baking pans (move lower to top, and top to lower), and then bake for 3 more minutes. Remove from heat.
In a large pan or skillet heat 1/2 cup butter on medium heat. Add 16 oz. sliced mushrooms, 4 chopped celery stalks, and 2 cups chopped carrots. Cook for about 10 minutes stirring often. Then add spinach and cook for another 2 minutes until it's wilted. Set aside.
In a medium-large bowl add 1 & 1/4 cups vegetable broth, replacements for 2 eggs, 1 tsp ground sage, 1/2 tsp dried thyme, 1/2 tsp onion powder, 1/4 tsp garlic powder, and 1 tsp dried marjoram. Stir well.
Put bread chunks in large baking dish, and top with broth mixture and vegetables. Season with salt & pepper if you desire. Stir well with a wooden spoon. Bake at 350 degrees for 50 minutes. Every 15-20 minutes you can take the stuffing out of the oven and give it a stir.