Jam lattice tart

Preheat the oven to 200°C, gas mark 6, and put a large baking sheet inside to preheat. Grease the base and sides of a separate 20x30cm baking tray. Cut off ⅔ of the pastry dough and roll out the larger piece on a lightly floured surface to form a rectangle measuring 25x35cm and about 0.2cm thick. Gently ease the pastry into the prepared tray. Scrunch a rectangle of baking parchment, lay it over the pastry and cover with baking beans. Put the tray on the preheated baking sheet and blind bake for 15 minutes, then remove the beans and parchment and bake the pastry crust for another 5 minutes.

While the crust cooks, prepare the lattice. On a lightly floured surface, roll out the remaining dough into a 20x30cm rectangle. Slice it into 1.5cm-wide strips about 0.2cm thick (or use a lattice roller). Arrange the strips on baking parchment, weaving over and under one another into a lattice; chill for 10 minutes. Meanwhile, in a bowl, stir together the jam and berries.

Remove the pastry crust from the oven and spoon over the jam mixture. Slide the lattice onto the filling and pinch the raw pastry onto the blind-baked sides. Brush with the beaten egg, return to the preheated baking sheet, then bake for 20-25 minutes, or until golden. Let stand for 15 minutes before slicing, then enjoy warm or at room temperature, with crème fraîche if liked.