Slab pies – like our Peach Blueberry Slab Pie – aren’t only fun to make; they feed a dozen or more, whereas your average 9-inch round pie feeds about eight.
The catch? You’ll need more dough to make the shell for your slab pie pan, namely a 15-inch by 10-inch by 1-inch tall jelly roll pan. But no problem: this bigger batch of dough is a cinch to mix in the food processor. (But if you DO prefer to make this by hand, instructions follow.)
First make sure to chill your dry mixture and your butter a good hour ahead. Mix the dry ingredients, and put them in the freezer. Cut your cold butter into 1/2-inch cubes, put them on a plate, and refrigerate for an hour. While you’re at it, get out your 1 cup glass measuring cup, fill it to the 1/2 cup mark with cold water, and refrigerate that too. After an hour you’ll be ready to proceed.
First pulse your dry ingredients with your cold butter, about 8 to 10 times, until the butter is the size of small peas. Then add your 1/2 cup water, down the feed tube in a 10-second stream, pulsing the machine as you add it. Pulse maybe 10 to 12 times, until you have small, uniform crumbs that hold together when you pack them in your palm, like in the photo below. (Check the consistency before you dump out the crumbs.)
Even though the mixture is crumbly, it can be packed like the clumps on the left.
Now gather and pack it all very loosely and put it in a 1-gallon plastic freezer bag, slightly off center so it favors the sealed edge opposite the side that opens. Fold over the open edge, to make more of a rectangle, then take your rolling pin and roll the pastry right in the bag out toward the edges. This will square off the sides of your pastry and make it easier to roll the rectangular shape you need for the pan. Refrigerate the pastry for at least one but preferably 2 hours. Here’s the dough in the bag, below.
After an hour or two, you’ll roll the dough into an 18-inch by 13-inch rectangle. Make sure your kitchen is cool before you start rolling. I’ll actually adjust the thermostat 30 minutes ahead to lower the temperature in the kitchen so it’s good and cool. Cut the bag with scissors to remove the dough. Roll it on lightly floured wax paper, between two sheets of plastic wrap, on a well-floured surface or parchment – whatever method you’re used to and works best. Then line the pan with the dough.
Don’t worry if you need to do a little patchwork here and there: you’ll never see it after the pie is baked. Trim, sculpt, and pinch the sides so they’re flush with the top of the pan. When you’re all set, put the pan in the refrigerator for an hour. Longer is fine.
Now you’re all set to fill and bake your pie. Good luck.