Summer is in full swing, and we are spending our days in blissful leisure: swimming, reading, bike riding, hiking, lego-building, canoeing, and the like. I’ve been able to sneak some baking into our full days; even with the temperatures hot as can be I’ve been enjoying getting into the kitchen and using all the seasonal summer fruit that is overflowing everywhere we turn. Slab pie is always a favorite – it works well with berries and can feed a crowd; perfect for BBQs and 4th of July celebrations. I always sneak some grated Gala apple in my pies; the sweetness helps reduce the overall sugar, and the added pectin from the apple lets me use less thickener.
A couple notes: this pie is a little on the tart side due to the blackberries. If that isn’t your thing, you can substitute 1/2 the blackberries with chopped strawberries or raspberries with good results. Reduce the sugar added to the saucepan to 1/4 cup (instead of 1/3 cup) if using sweeter berries. Your favorite pie crust will work here.
1 cup peeled and grated Gala apple, about 2 small apples
1 tablespoon lemon juice
1/2 cup (99g) granulated sugar, plus 1/3 cup, plus 1-2 tablespoons for sprinkling
1/4 teaspoon salt
2 tablespoons unsalted butter
1 teaspoon pure vanilla extract
1/4 cup cornstarch
egg wash (1 egg, 1 tablespoon water, and a pinch of salt whisked together)
Combine the blackberries, grated apple, lemon juice, 1/2 cup sugar, and salt in a large bowl. Let sit for 1 hour at room temperature.
Strain the sugary juice from the fruit into a medium saucepan (you should have at least ½ cup of juice). Return the fruit to the large bowl. Add the remaining 1/3 cup sugar to the juices in the pan and bring to a boil over medium heat. Simmer until reduced to a scant 1/2 cup, about 5-6 minutes, shaking the pan occasionally to stir. Remove from the heat and whisk in the butter and vanilla. Set aside to cool slightly.
Sprinkle the cornstarch over the fruit and toss to coat. Pour the slightly cooled fruit juice mixture over the fruit and stir gently.
to assemble and bake
Lightly flour a large sheet of parchment paper and roll out one piece of the dough into a 17 by 13-inch rectangle. Repeat with the second piece of dough. Using the parchment paper, transfer one rectangle to a 13 by 9-inch jelly roll pan or quarter sheet pan. Press the dough into the pan; discard the parchment.
Pour the filling on top of the dough and spread into an even layer.
Using the parchment paper, place the second rectangle of dough on top of the filling; discard the parchment. Trim the dough overhangs to 1 inch past the lip of the pan.
Pinch the dough together and tuck it under itself. Crimp the edges and cut several X-shaped vents across the top of the dough. Place the pan in the freezer for about 20 minutes while the oven is preheating. You want the crust to be nice and firm before you bake it.
Adjust an oven rack to the lowest position. Preheat oven to 425°F. Place a baking sheet on the oven rack (the preheated baking sheet helps crisp the bottom of the pie crust and catches any leaks and drips).
When ready to bake, brush the top of the pie with egg wash and sprinkle with 1 or 2 tablespoons of granulated sugar. Put the pie plate on the preheated baking sheet and bake 25 minutes. Reduce the oven to 375ºF and bake 40 to 50 minutes more, until the crust is deep golden brown and the juices bubble.
Transfer the pan to a wire rack and let cool at least 4 hours before serving.