Genius Slab Pie for the Fourth of July

Every week on Food52.com, we're digging up Genius Recipes -- the ones that make us rethink cooking myths, get us talking, and change the way we cook.

Today: How to stretch a pie to feed a crowd, with whatever fruit is in season near you. Happy 4th of July!

- Kristen Miglore, Senior Editor, Food52.com

There are a lot of ways to make a slab pie, and Martha Stewart, bless her, has made them all. She might have invented the whole genre.

>>RELATED: Martha also invented the best Macaroni and Cheese recipe. Check it out.

Now, if you haven't heard of slab pie, you're not alone -- it's surprisingly under the radar still. Let's change that.

A slab pie is simply a shallow pie that's made in a rimmed baking sheet, usually a jelly roll pan. It feeds more revelers than a standard 9-inch pie will, with less mess and fuss.

It's a pie in a sensible bar cookie outfit; a hand pie, without having to shape a bunch of hand pies; a boon to crust-lovers everywhere. It is, essentially, a Pop-Tart.

>>RELATED: How to Make Any Free-Form Fruit Tart in 7 Steps.

And I'm not kidding that Martha has made them all. She's published slab pies in strawberry-rhubarb, peach-raspberry, and quince. She's fluted and folded and twirled their edges, given them peek-a-boo slits and polka-dots.

In Martha Stewart's Baking Handbook, there is a pure distillation of all of these recipes: a slab pie template, for any fruit growing near you. Here we used mixed berries, because we're feeling patriotic.

>>RELATED: Just berries, sugar, and sliced bread: No-Cook Berry Pudding

Here are the bones of the recipe, with a lot of pictures:
Make a simple pate brisee in your food processor (or by hand).

Mix fruit with sugar, lemon, and salt, and cornstarch to thicken.

Roll out two wide sheets of dough.

Layer them in a jelly roll pan with fruit filling sandwiched between.

Paint the top with cream and rough it up with sanding sugar. Bake.

For the filling, you have a couple options. If you want to serve it on plates with forks, you can bump up the fruit amount -- it will be sloshy and ooze molten berries (or peaches or cherries) as you plate it. But if you want people to be able to snatch it up like a Pop-Tart while they mill around drinking, stick with 6 cups of fruit.

Most important of all, remember this thing is called slab pie -- it sounds like something Barney Rubble made. Rustic is a good look for it. Call it shabby caveman, and even Martha would approve.

Martha Stewart's Slab Pie

Adapted slightly from Martha Stewart's Baking Handbook (Clarkson Potter, 2005)

Makes one 15-by-10-inch pie

Slab Pie:

All purpose flour, for dusting
Pate Brisee (recipe below)
6 cups fresh sour cherries, stemmed and pitted; or 6 cups fresh mixed berries; or 7 medium peaches, cut into 1/2-inch pieces (about 8 cups)
1 1/4 cup granulated sugar
1/4 cup cornstarch
Juice of 1/2 a lemon (about 1 tablespoon)
1/4 teaspoon salt
1/4 cup sanding sugar (or granulated sugar)

1. Heat oven to 375 degrees F. On a lightly floured surface or between two large, floured pieces of plastic wrap, roll out larger piece of dough to an 18-by-13-inch rectangle, trimming excess dough. Fit into a 15-by-10-inch rimmed baking sheet, pressing into corners (pastry will hang over sides). Chill while assembling filling.

2. In a large bowl, stir together fruit, granulated sugar, cornstarch, lemon juice, and salt. Spread mixture over chilled pie shell. Chill again while you roll out the top crust.

3. On a lightly floured surface or between two large, floured pieces of plastic wrap, roll out remaining piece of dough to a 16-by-11-inch rectangle; drape over filling. Fold edge of bottom dough over top dough. Crimp if desired. Prick top dough all over with a fork. Brush entire surface of pie with cream (thinned with a little water if necessary), and sprinkle with sanding sugar.

4. Bake until crust is golden brown and filling is bubbling, 40 to 55 minutes. Transfer to a wire rack, and let pie cool until it is just warm to the touch, about 45 minutes. Serve warm or at room temperature, cut into 12 pieces. 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.

Slab Pie Pate Brisee:

5 cups all purpose flour
1 tablespoon coarse salt
2 teaspoons granulated sugar
1 pound (4 sticks) cold unsalted butter, cut into small pieces
12 to 16 tablespoons ice water

1. Process flour, salt, and sugar in a food processor until combined. Add butter. Process until mixture resembles coarse meal, about 10 seconds. With machine running, add ice water in a slow, steady stream just until dough comes together. (Do not process more than 30 seconds.)

2. Turn dough out in two portions onto two pieces of plastic wrap, with one slightly larger than the other (this will be your bottom crust). Flatten dough, and shape into rectangles. Wrap in plastic. Refrigerate at least 1 hour (or overnight).

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Photos by James Ransom