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 food processor or blender, then blend until smooth.
Add the cooked mushrooms and onions to the food processor, 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.