Crostata

Crostata is a tart of long standing in Italian cooking, and the word in its modern sense is documented from the Renaissance: a recipe for a crostata appears in Maestro Martino's «Libro de Arte Coquinaria» of around 1465, and the late-15th-century «Cuoco napolitano» gives one as well, as recipe number 94, «Crostata de Caso, Pane». The name comes from the Latin «crustata», from «crustare», to encrust, from «crusta», a crust; the term was current enough to be defined in the Accademia della Crusca's 1612 dictionary. Early crostate could be savoury as well as sweet; the now-standard home form — sweet pasta frolla filled with jam under a lattice — became the familiar version over later centuries. What sets a crostata apart from a French «tarte» or an English pie is precisely this open lattice top rather than a full crust.

The crust is the thing: pasta frolla bakes short and crumbly, snapping cleanly and then dissolving into a rich, buttery, faintly vanilla sweetness, never tough or chewy. Against it the jam is soft, glossy and concentrated, sweet-tart and fragrant — apricot, sour cherry, figs — having thickened and caramelized slightly at the edges in the oven. The lattice strips bake a shade crisper than the base. The balance is between the friable, almost sandy pastry and the sticky fruit. A good crostata holds a clean slice with the jam set, not runny; a bad one is either pale and raw-tasting or worked too hard so the pastry turns hard and biscuit-tough.

Pasta frolla is a short pastry, and its whole character depends on limiting gluten. Butter is rubbed or quickly worked into the flour so that fat coats the flour particles; this waterproofs them and keeps the gluten-forming proteins from joining into long, elastic strands, so the baked crust is tender and crumbly — short — rather than chewy. The dough is handled as little as possible and rested cold so any gluten relaxes and the butter firms, which keeps the pastry from shrinking and toughening in the oven. Egg yolks add fat and the emulsifier lecithin for richness and a fine texture. In the heat the butter melts and steams to leave a delicate crumb, while sugars in the pastry and at the jam's edges brown through caramelization. The jam needs to be thick: a runny one will boil, soak the base and prevent it crisping, which is why a set, concentrated fruit jam works best under the open lattice.