How to Make It
In a small saucepan, bring the favas, onion, potato and 4 cups of water to a boil over high heat, skimming as needed. Add the salt, cover loosely and cook over low heat until the favas are very tender, 1 hour. Let cool for 10 minutes.
Pulse the contents of the saucepan in a food processor until almost smooth. Scrape into a bowl, drizzle with olive oil and sprinkle with fleur de sel and pepper. Serve warm with crusty bread.