Set a large enameled cast-iron casserole over moderate heat for 1 minute. Add the sugar in an even layer and cook without stirring until melted and starting to caramelize, about 3 minutes. Stir in the duck fat. Add the onion, thyme, chile, allspice, 1 teaspoon of salt and 1/4 teaspoon of pepper. Cook over moderate heat, stirring often, until the onion is lightly caramelized, about 7 minutes. Stir in the wine and port and cook over moderately high heat until the liquid is reduced to 2/3 cup, about 5 minutes. Add the cabbage and accumulated juices and 1 teaspoon of salt. Cook over moderate heat, stirring often, until the cabbage is tender and glazed, about 20 minutes. Season with salt and pepper. Serve hot or warm.