Add your dehydrated mushrooms to your boiling water to re-hydrate. This will also create a delicious mushroom broth in the water, do not throw this out!
Slice your white mushrooms and portobello mushroom and set aside in a large bowl, along with your whole shiitake mushrooms. Once your mushrooms are re-hydrated slice those and add them to the mushroom bowl. Set aside the mushroom broth to be used later.
Mince your garlic and dice your white onion and add to a pan along with 1 tbsp of avocado oil. Sautee for about 3-5 minutes.
Once the garlic begins to brown add in your mushroom mixture and 1 tbsp of fresh thyme and toss until coated in oil. Sautee until all your mushrooms are tender, about 7-10 minutes.
Set your mushroom mixture aside and allow to cool.
Preheat oven to 350F.
Slice your stale baguette into cubes your desired size and add to a large bowl. Add in your mushroom mixture, sage, 1 cup of your mushroom broth, nutritional yeast and salt and pepper to taste. Mix until all the ingredients are evenly distributed.
Add your remaining avocado oil to a cast iron pan and using a paper towel coat all around the pan.
Add your stuffing to the cast iron pan and bake for 25-30 minutes. Broil your stuffing on medium for about 5 minutes. Watch carefully, because every oven is different and your food can burn very quickly.