In a large bowl, combine beans and water to cover by 2 inches; cover with plastic wrap, and refrigerate overnight.
In a large Dutch oven, heat olive oil over medium heat. Add onion, garlic, and rosemary; cook, stirring occasionally, until onion is tender, about 10 minutes.
Drain beans and add to pot along with broth, pepper, and salt. Bring to a boil over medium-high heat; reduce heat and simmer until beans are tender, 1½ to 2 hours. Discard rosemary sprigs.
In the container of a blender or using an immersion blender, process soup until smooth.
In a small bowl, stir together walnuts, rosemary, and lemon zest.
Ladle soup into bowls, and top with walnut mixture.
Recipe by Victoria at https://victoriamag.com/white-bean-rosemary-soup-recipe/