Russian tea cake is a kind of pastry, often eaten around Christmas in the United States. It is a form of jumble, a pastry common in England during the Middle Ages. They are little balls of buttery shortbread studded with walnuts and rolled in icing sugar. They're melt-in-the mouth moreish and, as the name suggests, an incomparable complement to a cup of tea. You can make the dough in advance and freeze for up to 2 weeks.