Pie is most commonly known as this round single or double crusted relative of cakes. They may interchangeably be called tarts, but pies tend to have a more heft filling than tarts. This particular type of pie, baked in a large rectangular rimmed dish and being double crusted is known as slab pie, but I disliked using the term slab in the title as it seemed crass to me.Regardless, slab pies are wonderful for feeding a large number of people, and this pie made 24 generous squares of pie. I used mulberries, but you can use any type of berries or even a mixture of berries. I also had a fair bit of extra dough when I trimmed the edges after placing the top crust over the fruit. I rolled the extra dough into a cylinder, covered it in plastic, and refrigerated overnight. Next day I sliced it while still cold into coins, placed it on a baking sheet, brushed it with egg wash and sprinkled it generously with sugar before baking it into cookies.
For the Crust:
7 cups flour
½ cup sugar
1 tsp salt
2½ cups butter, COLD, cut into pieces
1⅓ cups ice water
1 Tbsp white vinegar
For the Filling:
6 cups berries
1 cup sugar
1 lemon, zest and juice
2 Tbsp corn flour
First, make the crust: Whisk together the flour, sugar, and salt in the bowl of your food processor. Since this is a lot of dough I suggest making it in two batches.
Add in the chopped pieces of cold butter.
Pulse until you have coarse crumbs.
Mix together the water and vinegar in a small bowl. Slowly drizzle it over the dough as you are pulsing the food processor, until fully incorporated (you may not use all of the water).
Form the dough gently into 2 discs, wrap tightly in plastic wrap, and chill in the fridge for 2-3 hours or as long as overnight. Make your filling when you are almost ready to use your dough.
When you are ready to bake, preheat your oven to 400F.
Mix together berries, sugar, lemon zest, lemon juice, corn flour and set aside.
Generously butter a 9×13-inch rimmed baking sheet and set aside.
Flour your work surface, rolling pin and your hands. Take one ball of dough (leave the other in the fridge) and begin to roll it out to fit your baking sheet (about 13×18-inches so that you have some overlap over the pan).
Spread the berry mix over the bottom pie crust, then roll out the second crust and place it on top, gently folding and unfolding it to transfer to the pan.
Crimp the edges, cut away any extra dough, and cut some slits into the top crust (to let the steam vent out from the cooking fruit).
Beat an egg and brush the top of the crust with it, then (optionally) sprinkle generously with granulated sugar.
Place the pie in the oven, then immediately reduce the heat to 375F.and bake for 50-60 minutes, until golden and bubbling.
Allow the pie to cool almost completely before slicing and serving.