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Blueberry, Apple, and Caramel Pi Day Slab Pie

yield: 1 double-crust slab pie

Special Equipment

  • A food processor
  • numerical cookie cutters (see baker's notes)
  • a pastry brush


For the Pâte Brisée

    (makes 1 double-crust slab pie)

    • 2 1/2 cups all-purpose flour
    • 1 teaspoon granulated sugar
    • 1 teaspoon kosher salt
    • 1 cup (2 sticks) unsalted butter, cut into 1-inch cubes and frozen overnight (see baker's notes)
    • 6 tablespoons ice cold water
    • 2 tablespoons apple cider vinegar

    For the Blueberry, Apple and Caramel Filling

      (makes enough for 1 double-crust slab pie)

      • 3 cups fresh blueberries
      • 1 medium apple, cut into 1/2-inch cubes (approximately 1 cup)
      • 2 generous (small mound, unleveled) tablespoons cornstarch
      • 1/4 cup caramel sauce
      • a pinch of kosher salt

      For Assembly

        (makes enough for 1 double-crust slab pie)

        • 2 tablespoons unsalted butter, cut into small specks
        • 1 large egg
        • 1 generous (small mound, unleveled) tablespoon granulated sugar


        For the Pâte Brisée

        • In the bowl of a food processor, combine 2 1/2 cups all-purpose flour, 1 teaspoon granulated sugar, and 1 teaspoon kosher salt. Pulse for a few seconds until the ingredients are fully incorporated. Scatter 1 cup very cold cubed unsalted butter over the mixture, and pulse for a few seconds until the mixture resembles coarse meal, around 8 to 10 seconds total. DO NOT OVERPULSE.
        • In a small liquid measuring cup, whisk together 6 tablespoons ice cold water and 2 tablespoons apple cider vinegar. You should have 1/2 cup of liquid. Grab 2 ice cubes, stick them in the measuring cup and whisk them ferociously for at least 10 seconds to chill the apple cider vinegar before fishing them out.
        • With your food processor running, add 1/4 cup of the water and cider mixture in a slow, steady stream through the feed tube. Stop the machine when 1/4 cup is added, and pulse one or 2 times until the dough holds together — at this point, it's okay if the mixture still looks kinda dry and is just holding itself together with a few big chunks here and there. That's actually what you want. Use a rubber spatula to turn out the mixture into a large bowl. At this point, test the dough by squeezing a small amount together. If it is crumbly, sprinkle 1 tablespoon of water/apple cider (from the leftover mixture, you should have a cup left) and use your hands to mix until the dough comes together in a ball with some dry bits remaining. Squeeze and pinch with your fingertips to bring all the dough together, and, if necessary, sprinkle any dry bits with small drops of ice water to combine. Shape the dough into a flat disc, and use a bench scraper to divide it into two portions: one portion should be two-thirds of the dough (16 ounces, for those using a measuring scale), the other should be the remaining third (around 8 ounces). Wrap the portions in plastic and refrigerate for at least 1 hour, preferably overnight to give the crust time to mellow. Wrapped tightly, the dough can be refrigerated for 3 days or frozen for 1 month.

        For the Blueberry, Apple, and Caramel Filling

        • When you're ready to make out the pie, make the filling. In a medium bowl, combine 3 cups fresh blueberries and 1 cup apple chunks. Sprinkle 2 generous tablespoons cornstarch over the fruit, and use a rubber spatula to gently toss the fruit until completely coated in the cornstarch.
        • When the fruit has been dredged, drizzle 1/4 cup caramel sauce and a pinch of kosher salt over the mixture. Use your rubber spatula to toss the fruit until coated completely in caramel. Set aside while you roll out the pie dough.

        For Assembly

        • Prepare a large rimmed baking sheet (at least 15 x 10-inches) by lining with parchment paper. Set aside.
        • Liberally sprinkle a work surface with flour. Unwrap the larger portion of dough (the 2/3rds one) and place it on the work surface, sprinkling its top with flour. This portion will be your base crust. If the dough is hard, let it rest for a few minutes. If the dough seems too sticky at first, add flour liberally. Use a rolling pin to roll with light pressure, from the center out, moving the pie dough around every quarter to roll it evenly. Roll the the dough to a rough oval that is about 15-inches long, 10-inches deep, and about 1/4-inch thick. Transfer this oval onto the prepared baking sheet and refrigerate while you roll out the remaining disk.
        • Replenish your work surface with more flour. Repeat step 2, this time rolling the dough out to a smaller oval that is about 13-inches long and 9-inches deep. This portion will be your top crust. Transfer the rolled out dough on to a piece of wax or parchment paper. Use your numerical cookie cutters to stamp out the Pi number sequence, dipping the sharp edge of each cutter in flour before doing so. Once your numbers have been stamped, transfer the crust into the freezer to chill while you fill the bottom crust with pie filling.
        • Remove the base crust from the refrigerator and use a spoon or a rubber spatula to transfer the fruit filling to the center of the crust. Spread out the filling evenly over the base, but leave a 2 to 3-inch border all the way around the oval. Evenly dot the fruit filling with 2 tablespoons of unsalted butter specks.
        • Remove the top crust from the freezer and gently, carefully lay the crust over the fruit filling. There should still be a 1 1/2 to 2-inch border visible from the base crust. Working quickly, fold this border over the top crust, overlapping when necessary and pressing gently to adhere to the folds. Use a fork to press down on the border to "seal" and "crimp" the bottom crust onto the top crust. Transfer the pie to the refrigerator to chill while you preheat the oven.
        • Center a rack in the oven and preheat the oven to 375 (F). While the oven is heating, whisk 1 large egg in a small bowl.
        • When the oven is ready, remove the pie from the fridge. Working quickly, use a pastry brush to brush the top and border of the pie. Sprinkle evenly with 1 tablespoon granulated sugar and transfer immediately to the preheated oven. Bake until the crust is golden brown and filling is bubbling, 30 to 35 minutes. Transfer to a wire rack, and let pie cool until it is just warm to the touch, about 45 minutes. Slab pie is best eaten the same day it is baked, but it can be kept at room temperature, loosely covered with plastic wrap, for up to 2 days.