Double-Crust Blueberry Lemon Tarts

Steps

1. Make the pastry: whisk the flour, the salt and 15 g of the sugar in a large bowl.
2. Add the butter and rub it in with your fingertips until the pieces are the size of peas and flat flakes remain.
3. Drizzle in the water a little at a time, tossing with a fork, until the dough 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, toss the blueberries with 150 g of the sugar, the cornstarch, the lemon zest, the lemon juice and the cinnamon. Let it stand 15 minutes.
6. Preheat the oven to 425°F (220°C) with a rack in the lower third and a rimmed baking sheet on it.
7. Roll 2 of the dough disks into 11-inch rounds and fit them into two 9-inch tart or pie pans, leaving the edges overhanging.
8. Divide the blueberry filling between the two crusts, scraping in its juices.
9. Roll the remaining 2 dough disks into 10-inch rounds and lay one over each tart as a full lid. Trim, fold the edges under, crimp to seal and cut 4 steam vents in each lid.
10. Brush the lids with the egg and sprinkle with the remaining 20 g of the sugar.
11. Set the tarts on the hot baking sheet and bake 20 minutes, then lower the oven to 375°F (190°C) and bake 35 to 45 minutes more, until the crust is deep golden and the filling bubbles thickly through the vents. Tent with foil if the edges brown too fast.
12. Cool the tarts on a rack for at least 2 hours so the filling sets, then cut each into 6 slices.