Soak cashews in 1/2 cup hot water for 30-45 minutes. You can also soak overnight in water. But if you are like me and you forgot to soak overnight, just soak in hot water for 30-45 minutes.
Transfer soaked cashews along with the water to a blender. Blend to a smooth paste and set aside. This is cashew cream which will be used later in the recipe.
Press the saute button on the instant pot and then press adjust to set saute to "less".
Once it displays hot, add the oil and then add the garlic and the onion. Saute for 7 to 8 minutes, stirring often.
Then add the sliced mushrooms, stir and cook for 2 minutes.
Add the Italian seasoning, garlic powder, red pepper flakes, black pepper, white pepper and salt and stir.
Stir in the almond milk and water (or vegetable broth) and stir. Make sure there's nothing stuck at the bottom of the pot.
Break the lasagna sheets and add them into the pot. Press the lasagna sheets gently under the liquid using a spatula.
Close the pot. Press the manual or pressure cook button and cook on high pressure for 5 mins with the pressure valve in the sealing position. Let the pressure release naturally for 10 minutes and then do a quick pressure release.
Open the lid and press the saute button. Add the prepared cashew cream and stir.
Then add the lemon juice, nutritional yeast and stir. Lastly, add the fresh basil and let the soup simmer for 2 minutes.
Garnish with more basil and serve the vegan mushroom white lasagna soup hot!
The soup really thickens as it cools down (because of cashews) so it's best to serve it straight. If you want to serve it later, thin it down by adding more water before serving (add water while heating it up).
You may also add spinach to the soup for added flavor.