How to Make It
Combine beans, tomatoes, onion, bell pepper, broth, cumin, oregano, jalapeño halves, and 2¾ teaspoons of the salt in a 6-quart slow cooker. Cover and cook on LOW until beans are tender, about 8 hours.
Heat oil in a large nonstick skillet over medium. Add plantain slices in batches, and cook until golden brown, about 2 minutes per side. Transfer to a plate lined with paper towels, and sprinkle with remaining ¼ teaspoon salt.
Remove jalapeño halves from chili; stir in vinegar. Pour 1 cup of chili into a blender. Remove center piece of blender lid (to allow steam to escape); secure lid on blender, and place a clean towel over opening in lid to prevent splatters. Process until smooth, about 30 seconds. Stir back into unblended chili. Spoon chili into 6 bowls; top with plantains, and garnish with sour cream and scallions.