How to Make It
In a large saucepan or stockpot, combine 1 1/2 cups of the stock with the chipotles, onion and a generous pinch each of salt and pepper and bring to a boil. Add the collards in large handfuls, letting each batch wilt slightly before adding more.
Cover and cook over moderate heat, stirring occasionally, until the collards are just tender, about 25 minutes. Uncover and cook, stirring occasionally, until the broth is slightly reduced, about 7 minutes; discard the chipotles and the onion.
Meanwhile, in a small saucepan, combine the black-eyed peas with the remaining 1 cup of stock and bring to a boil. Simmer over moderate heat for 8 minutes; season with salt and pepper. Using a slotted spoon, add the black-eyed peas to the collards; reserve the bean broth for another use. Add the vinegar to the collard greens and season with salt and pepper.