Add the butternut squash and farro and cook for an additional 2 to 3 minutes over low heat, stirring occasionally.
Add the white wine and cook for 2 to 3 minutes, or until the wine has completely reduced. Add enough stock to cover the farro and squash and continue to cook over low heat, stirring frequently.
Continue adding small amounts of stock for about 18 minutes, or until farro is almost done cooking.
Stir in the mushrooms and cook for 3 to 5 minutes more.
Check for doneness (the farro should have a slight bite). When the farro is done, add the cashew cream, cheese, and butter (if using), stir, and then cook for a few minutes more until the cream starts to thicken.
Drizzle the risotto with white truffle oil. Taste and season accordingly.
Soak the cashews in the water for 24 hours. Then, place the cashews in a blender with water and blend until it is as smooth as possible. Strain through a sieve.