Boil the potatoes, carrots and onions with enough water for 10 minutes or until potatoes are cooked through.
Once cooked, drain the potatoes, carrots and onions and reserve the cooking water.
Add the cooked potatoes, carrots, onions, cashews, garlic, salt, onion powder, nutritional yeast, and a cup of water to a blender. Blend until the mixture is creamy, adding more water if necessary.