Dundee orange marmalade, made from bitter Seville oranges, is best for this dessert. Our favorite brand was James Keiller & Son Dundee Orange Marmalade. Whole-wheat breadcrumbs provide the pudding with both structure and flavor; we made our own from standard whole-wheat sandwich bread. Make sure to choose a loaf without added seeds or nuts. We highly recommend purchasing whole nutmeg and grating it just before use; the flavor is much better than purchased ground. The pudding can be served warm or at room temperature. Either way, it begs for a cool, creamy accompaniment. A rich, silky custard sauce spiked with scotch is traditional, but ice cream or lightly sweetened whipped cream would also be delicious.