Blackberry Slab Pie

Heat the oven (with the oven rack in the lower third of the oven) to 375°F. Line an 18 x 13-inch rimmed sheet pan with parchment paper, leaving a 2-inch overhang on the long sides. Tear off another piece of parchment the same size as the other.

For the double piecrust, you’re going to make it in two batches. In a food processor, combine 2½ cups of the flour, 1 tablespoon of the sugar, and ½ teaspoon of the salt. Cut 2 sticks of the butter into small pieces and add to the food processor. Pulse several times until the butter pieces are pea size. Add 7 tablespoons of the water and pulse several times until moist crumbs form and hold together when pinched. You may have to add 1 more tablespoon of water. Pour the crumbs into a ziptop bag then use the bag to gather it into a ball. On a floured surface, gently knead the dough a few times then shape it into a 1-inch thick rectangle. Put it back into the bag and refrigerate. Make the other piecrust with the remaining flour, sugar, salt, and butter. Refrigerate.

In a large bowl, toss together the blackberries, sugar, flour, and cinnamon.

To roll the bottom crust, place one piece of parchment on a work surface and dust it with flour. Place the first dough you made in the center of the parchment. Roll it into a large rectangle the size of the bottom of the sheet pan – it should be about ¼-inch thick. As you roll, you will need to dust the top of the dough as well underneath with flour to prevent sticking. Slide the parchment and dough onto the sheet pan. Pour the berries onto the dough, leaving a 2-inch border all the way around the dough. Refrigerate.

For the top crust, roll out the second piece of dough the same way you rolled the first one. Lift it off the parchment and onto the berries. Fold the edges of the dough over to seal. Crimp as you like. Lightly brush the top with the beaten egg and sprinkle with more sugar. Using the tip of a paring knife, make small slits in the top of the pie so steam can release while baking.

Bake until the crust is golden brown and the berries are bubbling, 1 hour to 1 hour 15 minutes. Serve at room temperature.