In a pot, heat the oil over medium-high. Cook the leek, stirring often, until tender, 2 to 3 minutes. Add the broth and beans; bring to a simmer. Add the broccoli; cook until tender, 5 minutes.
Working in batches, puree the soup in a blender. Return the soup to the pot. Add the zest and juice; season with salt and pepper. Heat over medium-high until warm, 2 minutes. Divide among bowls; top with the Parmesan and black pepper.