Add 1 cup cashews and 1 cup boiling water to a bowl.
Let the cashews soak for 1 hour, then drain and rinse.
Add 3 tablespoons extra virgin olive oil to a large pot along with 4 cups of chopped mushrooms, 2 cups chopped onions, 2 cloves chopped garlic and 1 tablespoon fresh thyme leaves.
Cook at medium heat, stirring frequently for 10 minutes or until golden and caramelized.
Reserve a few mushroom to use as a garnish, if desired.
Add the soaked cashews and 1 cup of cold water to a blender, then blend until smooth.
Add the cooked mushrooms and onions to the blender, then blend until smooth.
Add the mushroom cashew purée back to the pot along with the remaining 2 cups of cold water, 1 teaspoon salt, 1/2 teaspoon black pepper and 2 tablespoons nutritional yeast, then simmer on low heat until the soup is hot.