Porrusalda, a rustic leek and potato soup from Spain’s Basque Country, takes a few humble ingredients and transforms them into a light but satisfying meal in a bowl. Some versions are made with salt cod or meat, but ours is vegetarian. Carrots are classic in porrusalda; parsnips are not, but we like their nutty notes and earthiness. Use whichever you prefer, or even a mix. Leeks’ many layers trap dirt and sand, so be sure to thoroughly wash the sliced leeks, then drain them well in a colander so excess water doesn’t cause the steaming, which will delay browning. Serve the soup drizzled with olive oil, with warm, crusty bread alongside.