Blueberry Slab Pie

Introduction

Imagine the deep, sweet-tart flavor of wild blueberries, perfectly thickened and bubbling beneath a golden, flaky crust. This Blueberry Slab Pie is the perfect solution for feeding a crowd, offering all the charm of a traditional pie in an easy-to-serve rectangular format. You’ll love how the blend of cinnamon and nutmeg complements the bright berry filling, creating a dessert that’s both comforting and impressive.

Prep & Cook Time

Prep Time: 20 minutes

Cook Time: 90 minutes

Total Time: 1 hour 50 minutes

Servings: 20

Ingredients

• 8 cups wild blueberries
• 2 1/2 cups granulated sugar
• 1/4 cup lemon juice
• 3/4 cup instant tapioca
• 1/2 teaspoon ground cinnamon
• 3/4 teaspoon ground nutmeg
• pie crust (recipe for 2 double crust pies)
• granulated sugar (for dusting the top of the pie)
• egg wash

Instructions

1. Preheat your oven to 375°F (190°C). Grease or line a 10×15-inch jelly roll pan.
2. In a large mixing bowl, gently combine the wild blueberries, 2 1/2 cups granulated sugar, lemon juice, instant tapioca, cinnamon, and nutmeg. Allow the mixture to sit for 15 minutes so the tapioca begins to absorb the juices.
3. While the filling rests, roll out one portion of the pie dough into a large rectangle roughly 2 inches larger than your pan on all sides. Carefully transfer it to the prepared pan, pressing it gently into the corners and up the sides.
4. Pour the blueberry filling into the crust-lined pan, spreading it into an even layer.
5. Roll out the second portion of pie dough. Drape it over the filling. Trim any excess dough, leaving about a 1/2-inch overhang. Fold the top crust’s edge under the bottom crust’s edge and crimp to seal.
6. Cut several steam vents in the top crust with a sharp knife. Brush the entire top crust evenly with the egg wash, then sprinkle generously with granulated sugar for dusting.
7. Bake on the center rack for 90 minutes, or until the crust is a deep golden brown and the filling is bubbling vigorously through the vents. (If the edges brown too quickly, cover them with foil strips.)
8. Transfer the pan to a wire rack and allow the pie to cool completely, at least 3-4 hours, to allow the filling to set fully before slicing into squares.

Variations

• Streusel Topping: Omit the top crust. Instead, crumble a mixture of brown sugar, flour, and butter over the filling before baking.
• Mixed Berry: Swap half the blueberries for other berries like raspberries or blackberries for a more complex flavor profile.
• Mini Hand Pies: Use the same filling and crust to create smaller, individual hand pies—perfect for on-the-go servings.
• Serve with Flair: Accent each warm slice with a dollop of whipped cream, a scoop of vanilla ice cream, or a drizzle of lemon glaze.

Tips for Success

• Allow Time to Set: Resisting the urge to cut into the pie while warm is crucial. The instant tapioca needs time to cool and thicken fully.
• Prevent Soggy Bottoms: A hot oven is key. Ensure your oven is fully preheated and bake the pie on the center rack for proper air circulation.
• Seal the Edges Well: A good, tight crimp on the crust edges is essential to prevent juicy filling from leaking out during the long bake.

Storage & Reheating

Store leftover pie, covered, at room temperature for up to 2 days or in the refrigerator for up to 5 days. For best results, reheat individual squares in a 350°F oven for about 10 minutes to recrisp the crust, or warm gently in the microwave for 20-30 seconds.

FAQ

Can I use cornstarch instead of instant tapioca?

Yes, you can substitute an equal amount of cornstarch. The texture will be slightly less clear and may set a bit softer.

Why wild blueberries?

Wild blueberries are smaller and have a more intense, tangy flavor than cultivated ones. If using larger cultivated berries, you may want to slightly increase the tapioca by 1-2 tablespoons.

What is the best way to roll such a large piece of dough?

Roll the dough on a large piece of lightly floured parchment paper. This makes it much easier to lift and flip into the pan.

My filling is bubbling over. What can I do?

Place a foil-lined baking sheet on the rack beneath the pie to catch any drips. This is a good precautionary measure.

Can I make this pie ahead of time?

Absolutely. You can prepare the filling and dough the day before. Keep the filling covered in the fridge and the dough discs wrapped in plastic. Assemble and bake the day of serving.

Do I have to use an egg wash?

No, you can use heavy cream or milk as a substitute. The egg wash provides the richest golden color and shine.