Place cashews in a bowl and cover with water. Let the cashews soak for one hour.
After an hour, drain the cashews. Add to a high speed blender along with ½ cup of filtered water and the nutritional yeast. Blend on high until creamy. Stop and scrape down the sides of the blender, as required.
Prepare the onions, garlic and carrots and have the rest of the ingredients on hand.
Prepare the mushrooms by removing the stems and scraping out the gills (the dark part). This should leave enough room to hold the filling.
Place the mushrooms, top side down, in a heavy slillet or glass pan and set aside.
Preheat oven to 350°F.
Heat olive oil in a large pan. Add the onions, garlic, carrots, sea salt and thyme to the pan sauté on medium heat, stirring occasionally for about 7 minutes. You can also add a small amount of pepper if you wish.
While the aromatics are cooking, wash, chop and dry the spinach.
Once the vegetables are tender, add ¼ cup of the veg stock and cook for another minute.
Add the spinach and cook until the spinach is wilted (about 4 minutes), stirring frequently.
After a minute, add the cashew cream, lemon juice and coconut aminos. If you do not have coconut aminos, you can swap with tamari. The coconut aminos, in addition to adding a Unami flavour, also adds a little bit of sweetness. The tamari will be saltier.
Cook the mixture for a couple of minutes, stirring often. This mixture should be fairly thick - thick enough to hold together when placed in the mushrooms.
Divide the spinach mixture over the four mushrooms. Sprinkle the dried breadcrumbs evenly over the mushrooms.
Place the mushrooms in the oven and bake for 30 minutes.
These mushrooms are great served over a grain such as Farro or quinoa with a side vegetable such as broccoli or green beans to complete your meal.