The salted cooking water seasons these beans perfectly. Add a squeeze of lemon while you’re blending the spread for extra zing.
In a large pot over high heat, bring 6 cups salted water to a boil. Add butterbeans, return to a boil, and cook for 10 minutes. Drain, then run butterbeans under cold water. Drain thoroughly.
Transfer butterbeans to the bowl of a food processor. Add sour cream, mint, parsley, lemon zest, and garlic and puree for 40 seconds. Scrape down sides of bowl, then continue to puree, slowly streaming in olive oil. Season to taste with black pepper. Serve with endive leaves or an assortment of vegetables and chips.