Lemony Raspberry Blueberry Lattice Pies

Steps

1. Make the pastry first: whisk the flour, 24 g of the sugar and 7 g of the salt in a large bowl.
2. Toss the cold butter into the flour mixture and rub or cut it in until most pieces are the size of peas, with some flat, larger flakes left.
3. Drizzle in the ice-cold water a little at a time, tossing with a fork until the dough just holds together when squeezed.
4. Divide the dough into 4 equal pieces, flatten each into a disk, wrap and chill for at least 1 hour.
5. While the dough chills, make the filling: in a large bowl stir together 260 g of the sugar, the cornstarch, the remaining 1 g of salt and the lemon zest.
6. Gently fold the raspberries, blueberries and lemon juice into the sugar mixture; let it stand 15 minutes so the juices start to flow.
7. Roll 2 of the dough disks into 12-inch rounds and fit them into two 9-inch pie plates, leaving the overhang. Chill while you roll the lattice.
8. Roll the remaining 2 dough disks into 11-inch rounds and cut each into 1-inch strips.
9. Divide the berry filling evenly between the two pie shells, scraping in all the juices.
10. Weave half of the strips over each pie in a lattice, trim, fold the bottom overhang over the strip ends and crimp. Chill both pies for 30 minutes.
11. Preheat the oven to 425°F (220°C) with a rimmed baking sheet on the lower rack.
12. Brush the lattice and edges with the beaten egg and sprinkle evenly with the remaining 16 g of sugar.
13. Set the pies on the hot baking sheet and bake 20 minutes, then lower the oven to 375°F (190°C) and bake 45 to 50 minutes more, until the crust is deep golden and the filling bubbles thickly through the lattice; tent the edges with foil if they brown too fast.
14. Cool the pies on a rack for at least 3 hours so the filling sets, then cut each pie into 6 slices.