Blend the cashews with 1/2 cup water and the nutritional yeast. Set aside.
Heat 2 cups water. Season with salt, ground pepper, tamari or soy sauce or aminos, and sage. Bring to a boil and slowly add in the polenta or cornmeal, whisking as you add it so lumps don't form.
Turn the heat to low and continue cooking the polenta for 10 minutes, stirring frequently. If the mixture gets too dry, add some water but don't make it too watery. You want the polenta to be fairly thick and it should be a bit of a workout for your arm when you stir.
Once the polenta is cooked, add the cashew cream and yeast mixture. Stir it in well. Turn off the heat. The cashew cream will help keep the polenta creamy even when it cools down.
Blend the cashews with an equal quantity of water into a smooth cream.
Soak the dry mushrooms in 1 cup of water for 30 minutes.
Heat the oil in a skillet. Add the garlic and saute, stirring, for a few seconds until the garlic gets very lightly golden. Add the fresh mushrooms and the dry, reconstituted mushrooms. Squeeze out all the water they were soaked in and reserve it for the sauce.
Saute the mushrooms for about five minutes and add the wine. Let the mushrooms cook over medium-high heat until the moisture has evaporated, then add the sage, thyme, ground black pepper, soy sauce or tamari or aminos, and stir to mix.
Add the reserved mushroom stock and let it cook down over medium-high heat for 3-4 minutes. Add the cashew cream and heat through. Check seasoning and add salt and pepper if needed.
Put the creamy polenta in bowls and ladle the mushroom gravy over the polenta. Serve hot or warm.