Linzer Torte (Hazelnut Pastry Tart with a Lattice of Jam)

Variations

• The jam: redcurrant is the most traditional; raspberry, plum and apricot are all used, and ko.wikipedia lists exactly that set.
• The nut: hazelnut is the default, walnut and almond both work. Almond is milder, walnut carries a faint bitterness.
• Linzer Augen: the same dough baked as biscuits, sandwiched with jam and cut with a window in the top. The American "Linzer cookie" is this.
• Without a lattice: crumble the dough over the top instead. Far easier to handle.
• An old recipe: the version in a 1653 manuscript cookbook is generally cited as the oldest surviving written cake recipe. In the nineteenth century it was posted in boxes as a gift, precisely because it keeps.

Tips

• A third of the flour is nuts. Dough and gluten says "fat gets between gluten strands and tenderises" — and here that fat is inside the nut. It is not something you control by temperature the way you control butter; it is simply present. At the same time there is less flour, so gluten is cut from two directions at once.
• A different kind of short from scones or a Cornish pasty. Those rub cold butter into a wheat dough. This replaces the flour itself, so however carefully it is handled it will never cohere the way a wheat pastry does.
• The lattice is not decoration. This dough cannot be lifted over the jam in one sheet. Cut into strips, each piece only has to travel a short distance — and if the strips tear you can pipe them instead. Apple pie uses a lattice to vent steam and could take a solid lid; here there is no such option.
• Cold, and between paper. Those two things are the whole of handling it. Five minutes at room temperature and it sticks to everything.
• The jam has to be thick. A runny jam boils in the oven, soaks the base and floods out between the strips. If a shop jam is loose, reduce it for five minutes and cool it. Half the reason redcurrant and raspberry are traditional is that they are high in pectin and set firm.
• Go light on the clove. Cinnamon and clove are what make a Linzer a Linzer, but a little too much clove tastes medicinal. A quarter teaspoon is plenty.
• Bündner Nusstorte puts its nuts somewhere else. There, caramelised walnuts are sealed inside an ordinary pastry. Here the nuts are in the pastry itself, and the top is left open.