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Blueberry Buckwheat Slab Pie

Blueberry Buckwheat Slab Pie

By: Sylvia Cummings (Read Bio)

Blueberry Buckwheat Slab Pie

This slab pie with a delectable crumble topping was shared with us by Ari Smolin who adapted it from Claire Saffitz's “Dessert Person.” It pairs earthy buckwheat with sweet summer blueberries—soil and sun in pastry form! Well-suited to feeding a crowd, it’s a substantial slab pie that travels well and disappears quickly!

Ari Smolin writes and edits for Milk Street’s magazine and cookbooks. Before joining the team, she baked her way from Brooklyn to Los Angeles—laminating croissants before dawn, shepherding sourdough loaves by the hundreds, and discovering that stone-milled flour plus seasonal fruit is her happy place. She writes about whole-grain baking as well, most recently co-authoring “Morning Baker: Recipes and Rituals for Breakfast and Beyond” with Roxana Jullapat. You can find her fruit-and-grain escapades on Instagram @ari.smolin.

Yield: 1 quarter sheet pan,  9" x 13"

Total Time: 5 hours, including dough refrigeration times 

Ingredients

For the crust:

For the crumble:

For the filling:

  • 800 g (1 3⁄4 pounds) fresh or frozen blueberries
  • 30 g (3 ½ tablespoons) cornstarch
  • 100 g (1 cup) white sugar
  • 26 g (2 tablespoons) dark brown sugar 
  • 14 g (1 tablespoon) fresh lemon juice 
  • ½ tablespoon vanilla extract

Instructions

  1. To make the crust: In a stand mixer with the paddle attachment, combine the flours, sugar, and salt. Mix on low speed for a few seconds to combine, then turn off the mixer and add the butter. Mix on the lowest speed until the butter pieces are about the size of walnut halves, 30 seconds to 1 minute.
  2. Drizzle in about half the ice water, then mix (still on the lowest speed) for 5 to 10 seconds. Stop the mixer and squeeze together a handful of dough. If there are bone-dry patches or the dough doesn’t hold together when squeezed, drizzle in a few more tablespoons of water, mix for a few seconds, then try squeezing again. Flour is variable and the water amount needed will change from one batch to the next. You want a mixture that is still crumbly but that clumps together easily when squeezed. The flour should be evenly moistened and a shade darker than when you started.
  3. Place a large sheet of plastic wrap on your work surface, then transfer the dough onto it. (Reserve the bowl and paddle to make the crumble -- no need to wash.) As you transfer the dough onto the plastic wrap, begin compacting it into a roughly 1-inch-thick rectangle. If there are crumbly portions, squeeze them together as you pack them onto the dough mass. 
  4. Wrap the dough tightly, then use your hands or a rolling pin to smush into an even layer. At this point, you can massage any remaining crumbly spots a bit to incorporate them into the dough mass. Refrigerate at least 1 hour before using. 
  5. To make the crumble: In a medium skillet over medium heat, toast the oats, stirring every 15 to 30 seconds, until fragrant and light golden brown, 3 to 5 minutes. Keep an eye on any smaller bits at the bottom of the skillet, which will burn if not moved around enough. Remove from the heat and let cool completely. (NOTE: This step is optional, but I love the deep, toasty cereal flavors it adds.) 
  6. In the reserved mixer bowl, combine the cooled oats, flours, sugars, salt, and butter. Mix on low speed until evenly moistened and clumping together with no visible dry spots. Refrigerate until ready to use. 
  7. Heat the oven to 425°F with a rack in the bottom position. To avoid a buttery, smoky situation, line the oven rack with foil. If you have a baking steel, place it on the rack. Otherwise, place an empty half-sheet pan on the rack. (A preheated flat surface to land your pie on will ensure that the bottom crust sets quickly and turns out crisp.) 
  8. To begin building the slab pie: Remove the dough from the refrigerator and let stand at room temperature for 5 minutes to soften. Unwrap and place on a lightly floured surface. Dust the top with flour. Roll the dough into a roughly 11-by-17-inch rectangle, then carefully slide it onto a 9-by-13-inch quarter-sheet pan. 
  9. Center the dough on the sheet pan. Working one side at a time, lift the dough up, then press it into the bottom of the pan. Push it all the way into corners, then up the sides of the pan. Trim any ragged or uneven edges, leaving at least ½-inch overhang. Fold the excess dough over itself to form an edge, then crimp as desired or leave the edge raw. Pop the crust into the refrigerator or freezer while you mix the filling. 
  10. To make the filling: In the largest bowl you have, combine the blueberries, cornstarch, sugars, lemon juice, vanilla, and salt. Toss until evenly coated. 
  11. To assemble: Remove the crust and crumble from their chilly spots. Scrape the blueberry mixture into the crust, then pat into an even layer. Scatter the crumble in an even layer over the blueberries, using your hands to break up any pieces larger than a pecan. 
  12. To bake: Transfer the assembled pie onto the preheated baking steel or sheet pan. Be careful; it’s heavy and large! Bake for 20 minutes, then reduce the oven to 350°F and continue to bake until the filling is bubbling and thickened. It’s important that the bubbles are rolling slowly, more like hot jam or syrup than hot juice. This could take anywhere from 1 hour to 1½ hours. If the crust starts getting dark in spots, cover it with foil. 
  13. Transfer the pie to a wire rack and let cool for at least 1½ hours before slicing. Be sure to hold your face over the pie and inhale deeply for a blueberry facial.

Posted on October 13 2025