In a medium bowl, add cashews and enough water to cover. Soak for 4 hours, or up to 12 hours, until they have softened. This will help to blend cashews into a fine paste. (If you don’t have a high-powered blender, the closer to 12 hours the better.)
In a large pot of boiling salted water, cook pasta according to package instructions. Drain and set aside.
Blend cashews, garlic,½cup water, and olive oil on high for 1 to 2 minutes, or until mixture is completely smooth. Transfer mixture to a small saucepan and heat on medium-low for 1 minute, or until mixture is warm.
Add Parmesan and yeast, stirring to incorporate.If sauce is too thick, gradually add water, stirring to combine, until desired thickness is reached.
Season sauce to taste with salt and a generous amount of fresh black pepper. Add boiled pasta to sauce and toss to coat.