In a large pot, saute your onion and garlic in the coconut oil for a few minutes, just until onions are softened.
Add potatoes to the pot along with the 7 1/2 cups water. Allow to simmer for 10-12 minutes, or until potatoes are fork tender. Once potatoes are tender, or close enough, add corn kernels and (if using frozen) cook for another few minutes until thawed.
Heat 1 1/2 cups water with vegan bouillon cubes for 1-2 minutes in the microwave (or in a small saucepan on the stove top if you prefer).
In a high speed blender, process 3-4 cups of the soup (make sure to get plenty of potatoes, corn, and onion), water/bouillon mixture, cashews, and nutritional yeast until smooth (if you have a Blendtec, use the Soup button). Pour blended mixture back into the pot and stir until well incorporated.