Combine the vinegar and 1 cup/250 ml water in a large bowl. Add the kid and soak for 2 hours. Drain well.
Heat the pancetta and butter together in an ovenproof casserole over medium heat. Add the carrot, onion, and nutmeg. Sauté until the onion is translucent, then add the meat. Cook very gently over low heat for 20 minutes until the meat is browned on all sides.