Blueberry-Rhubarb Slab Pie

Name: Blueberry-Rhubarb Slab Pie
Total time: 1 h 45 min
Yield: 10 servings
Cuisine: american
Ingredients: 2 1/4 cups/290 grams all-purpose flour, plus more for rolling; 3 tablespoons granulated sugar; 1 teaspoon kosher salt; 1 cup/225 grams cold unsalted butter (2 sticks), cut into pieces; Ice water, as needed; 10 ounces/290 grams fresh rhubarb, cut into 1/2-inch pieces (about 2 1/2 cups); 4 1/2 cups/600 grams fresh blueberries; 1/3 cup maple syrup; Pinch of kosher salt; 3 tablespoons cornstarch; 1/4 cup/60 grams chopped crystallized ginger; 1 large egg, beaten; 3 tablespoons sparkling or sanding sugar

By Samantha Seneviratne

Total Time: 1 hour 45 minutes, plus chilling and cooling
Rating: 4(189)
Notes: Read community notes

This slab pie is perfect for a party because it’s easy to transport, and it serves a crowd. Convenience aside, the true draw of this sheet-pan pie is the flaky, buttery crust and its rhubarb, blueberry and crystallized ginger filling. Cooking the fruit ahead of time results in a filling that is juicy but not soupy — and prevents the crust from absorbing too much liquid. Preparing the pie dough in the food processor is effortless and helps keep the butter cold, which leads to a flakier crust, but be careful not to over-process: Stop when the mixture is moist but still crumbly.

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Ingredients

Yield:10 servings

For the Pastry

2¼cups/290 grams all-purpose flour, plus more for rolling
3tablespoons granulated sugar
1teaspoon kosher salt
1cup/225 grams cold unsalted butter (2 sticks), cut into pieces
Ice water, as needed

For the Filling

10ounces/290 grams fresh rhubarb, cut into ½-inch pieces (about 2½ cups)
4½cups/600 grams fresh blueberries
⅓cup maple syrup
Pinch of kosher salt
3tablespoons cornstarch
¼cup/60 grams chopped crystallized ginger

To Finish

1large egg, beaten
3tablespoons sparkling or sanding sugar

Ingredient Substitution Guide

Preparation

Step 1
Prepare the pastry: In the bowl of a food processor, combine the flour, sugar and salt. Add the butter and pulse until the mixture is the texture of coarse sand with some larger pieces of butter. Drizzle in ⅓ cup ice water and pulse the mixture about 5 times or until the mixture is crumbly, but evenly moistened and holds together when you squeeze a bit in your hands. Add up to 3 more tablespoons ice water, but stop before the mixture becomes too wet.
Step 2
Tip the mixture out onto a large piece of plastic wrap. Using the plastic wrap, press the crumbs together. Divide the dough into thirds; tightly wrap one portion in plastic wrap, then combine the other two portions and wrap that larger piece of dough well in plastic wrap. Use a rolling pin to press both dough portions into two flat rectangles. Chill for at least 2 hours. (You can chill dough for up to 3 days in the fridge or freeze it for up to 3 months.)
Step 3
Meanwhile, prepare the filling: In a small saucepan, combine the rhubarb, 3 cups blueberries, the maple syrup and salt. Cook the mixture over medium heat, stirring occasionally, until the rhubarb has started to break down and the blueberries have started to release some of their juices, about 10 minutes.
Step 4
Transfer a few tablespoons of the liquid from the saucepan to a small bowl. Add the cornstarch and whisk until dissolved. Return the cornstarch mixture to the pan and cook, stirring, until the blueberry mixture has thickened, 2 minutes. Remove the pan from the heat and stir in the remaining 1½ cups blueberries and the ginger. Let this mixture cool completely.
Step 5
On a lightly floured piece of parchment, roll the larger portion of dough into an 11-by-13-inch rectangle. Trim the edges into straight lines. Transfer the parchment with the dough to a rimmed baking sheet. Roll the smaller portion of dough out to a 7-by-15-inch rectangle on a floured piece of parchment. Using a fluted pastry wheel or a sharp knife, cut the dough lengthwise into seven 1-inch-thick strips.
Step 6
Spread the filling over the uncut rectangle, leaving a 1-inch border on all sides. Lay the strips of pastry over the filling on the diagonal, spacing the strips about ½ inch apart. Trim the strips so that they are even with the edge of the rectangle. Fold the edges up and over the filling and the strips and press the corners to seal. (Press with the tines of a fork, if desired.) Wrap lightly with plastic wrap and freeze for at least 30 minutes (and up to 2 hours).
Step 7
Heat the oven to 400 degrees. Using the parchment, transfer the chilled pie to another rimmed baking sheet. (You don’t want to bake it on the cold sheet.) Brush the beaten egg all over the pastry and sprinkle with sanding sugar.
Step 8
Bake until the pastry is deep golden brown and the filling is bubbling in spots, 50 to 60 minutes. Transfer pan to rack to cool for at least 1 hour before slicing.

Ratings

4 out of 5

189 user ratings

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Cooking Notes

Caroline4 years ago

Actually, I always roll my pie crust on plastic wrap because you can easily see the size and where you need to roll out more, as well as it easily removes from the wrap into the pan.

Mik_Pa5 years ago

As I was making this I regretted every step starting with the decision to make it. To be honest I read through the recipe as i was assembling it. Before baking I decided I would never again try it. Then, even with all the fumbling it was pretty awesome. Loved the ginger and the filling was better tasting than I expected and just sweet enough. Finished the top of the dough with turbinado sugar. Really nice and won't be as troublesome second time around.

iesd3 years ago

I was surprised to read so many complaints in the comments! I’m not a confident baker and what I liked best about this pie, was that it didn’t have to look pretty to taste great. I wasn’t able to roll the dough out large enough, and that was totally fine! For my second go-round, I plan to double (or at least 1.5x) the crust recipe. DO NOT SKIP the candied ginger! It was a wow factor for me and my family. Even my partner, who strongly dislikes ginger, thought it added great complexity.

sue1 year ago

Just a fun concept! Love the filling and crust. Made it for a block party, cut it into squares and put it in decorative cupcake papers. It was a hit.

SS1 year ago

Halve sugar instead of quarter Make in regular pie dish with striped design

Barbara2 years ago

Delicious and gorgeous! Had more rhubarb, fewer blueberries, same total weight. Ginger was lovely complement to the fruits. I bake a lot: pastry was one of the lightest, flakiest I've ever made, even though I used plenty of flour to keep dough from sticking. It might be difficult to handle if not refrigerated as the recipe calls for. Fluted pastry wheel = pretty edges. Plenty of dough as written: made (2) 8" square pies, cut each into six pieces, ample servings. Don't understand the complaints!

Josie3 years ago

Does this work as hand pies?

Joe3 years ago

Most people loved the ginger, but a couple found that it overpowered the fruit for them. I always roll pastry dough between plastic worked great for this pne

iesd3 years ago

Nancy Tennent4 years ago

I found making the crust extremely laborious. Filling was tasty, but I won't make this again.

crust4 years ago

I’d like to use strawberries in stead of blueberries... any alterations necessary ? Increased liquid from strawberries?

patti4 years ago

I’d like to use strawberries? Any alterations necessary?

Diane4 years ago

It’s a good tip to roll out between plastic wrap (multiple overlapping sheets to give yourself space for 11/17” ), esp. if you are cooking in a 95° kitchen. My pie was so rustic I didn’t bother with egg wash and sugar sprinkle. Big hit anyway— ugly delicious isn’t ever bad. And the crust was quite strong -easy for people to grab their own square yet good texture and flavor; nice for not having to touch a pie server at an attempted social distancing gathering. More blueberry than rhubarb.

NCB5 years ago

Loved the blueberries and rhubarb - didn't have the candied ginger on hand but will try next time. I found I had to keep putting the dough back in the fridge every few minutes to separate from the parchment. It will get too pliant very quickly. Just take your time with the strips.

Alexandra5 years ago

This pie was delicious! The use of crystallized ginger was a nice contrast to traditional pies. The crust was also great, but I found it a little difficult to roll out. Even though I chilled for the recommended two hours, the dough became quite sticky as I rolled it out. I'd recommend using a lot of flour, and perhaps finding a way to chill the rolling surface and rolling pin (maybe rolling out on parchment paper on top of a chilled baking pan?)

Caroline4 years ago

Actually, I always roll my pie crust on plastic wrap because you can easily see the size and where you need to roll out more, as well as it easily removes from the wrap into the pan.

Mik_Pa5 years ago

SC5 years ago

The ginger turned out weird tasting against the mild blueberry and tart rhubarb. It’s too earthy and heavy to mix well in this berry mix. Disappointing.

MNbaker5 years ago

Pie was an interesting mix of fruits, though not sure about the ginger. Didn’t dislike exactly but wasn’t a stroke of genius like I thought it’d be. Crust and pie overall came out quite well, just not sure if it’s a blend that I’m necessarily a fan of. Also-i didn’t chill the dough/pie for nearly the time required and it turned out just fine—save yourself some time!

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