In a bowl, cover the cashews with water and let sit at least 4 hours. Then drain and pat dry. Combine all ingredients in a Vita-Mix or high-powered blender or food processor. Only if using stevia, add 4 tablespoons water. Blend until a super-smooth texture is achieved. Taste and add more sweetener until desired taste is reached. Pour into a prepared pie crust (see below the next photo for a crust recommendation), and freeze.