Pour the olive oil into a large pot and turn to medium heat. Add the diced yellow onion and sauté for about 3 minutes, stirring frequently. Add the garlic and continue to cook for about one more minute.
Add the vegetable broth, the peeled and diced potato, your well-rinsed beans, salt, pepper, and cumin. Bring to a low boil.
Continue to cook on a low boil for about 30 minutes.
Remove from heat and add the spinach. Let cool slightly (be careful not to burn yourself!) and use an immersion blender. Blend until you have a smooth and creamy consistency.
If you don’t have an immersion blender, wait until your soup has cooled down quite a bit and add to a regular blender. Be sure to let it vent a little at the top if your soup is still warm. Blend and then return to pot to reheat before eating. This soup can be stored in the fridge for up to five days.