Preparation Simmer lima and green beans, water, broth, scallions, cumin, cayenne, and 1 teaspoon salt in a large saucepan over medium heat, covered, until beans are tender, about 15 minutes. Purée mixture in batches in a blender until very smooth (use caution when blending hot liquids). Force purée through a fine-mesh sieve into a bowl, discarding solids. Chill (covered once cool) until cold, about 1 hour. While soup chills, purée herbs with oil and 1/4 teaspoon salt in cleaned blender. Season soup with salt and pepper. Serve with herb oil swirled in. Cooks' NoteSoup, without herb oil, can be chilled up to 2 days. Add herb oil just before serving.