Soak the cashews: Place the cashews (and date, if using) in a medium bowl and add 2 cups of the water. Set aside uncovered at room temperature for 10 to 12 hours. The cashews are ready when they break apart when pressed between two fingers.
Drain and add fresh water: Drain the soaking water from the cashews. Add the drained cashews (and date, nutritional yeast, or lemon, if using), remaining ½ cup water, and salt to a blender.
Blend into cream: Blend on high speed until completely smooth, about 3 minutes. Stop scrape down the sides of the blender and process again for 1 minute.
Store or use: Use immediately or transfer to an airtight container and refrigerate for up to 1 week.
