Baby Lima Soup with Chipotle Broth

INGREDIENTS

• 1 pound dried baby lima beans, picked over and rinsed
• 10 cups water
• 1 head garlic, top lobbed off to expose the cloves and loose skins removed
• 2 tablespoons olive oil or clarified butter
• 1 onion, halved top to bottom and sliced into thin crescents
• 1 to 2 chipotles in adobo sauce
• 2 teaspoons fine-grain sea salt
• Squeeze of lime juice (optional)