Slab pies are shallower than regular pies, but they make up for it in width. A 13 x18 sheet pan pie will easily feed 12 people, perfect for a party. While conceivably you could use a prepackaged folded frozen pie crust (just get four of them and cut them to fit the rectangular sheet pan, and cut out the shapes), I strongly encourage you to try the home made crust recipe I’ve included for this pie. It’s my favorite pie crust recipe. It’s really easy to make, easy to roll out, requires no special equipment, and you don’t have to keep everything cold (actually room temp is best for this recipe). You just need clean hands, flour, sugar, salt, butter, and wait for it…sour cream! The sour cream adds moisture and fat to produce a wonderfully flaky crust. For the filling for this flag pie we are using blueberries for the stars blue background and strawberries for the red stripes. You could easily substitute and switch it up a bit with blackberries for the stars and rhubarb, cherries, or raspberries for the stripes. While this recipe calls for blueberries and strawberries, you can easily change it up a bit. Add raspberries, cherries, or rhubarb to the strawberries or use blackberries instead of or in addition to blueberries. As you are rolling out the dough for the crust and stars and stripes, if it becomes too too soft to handle, just put it in the refrigerator for a few minutes.
3 1/2 cups all-purpose flour 3 1/2 teaspoons sugar 1 1/2 teaspoons kosher salt 14 ounces butter (3 1/2 sticks), cut into cubes 7/8 cup sour cream (that’s 3/4 cup plus 2 tablespoons)
Strawberry filling:
3 1/2 pounds strawberries, hulled, quartered 1/2 cup sugar 2 teaspoons orange zest 4 tablespoons cornstarch, flour, or minute tapioca
Blueberry filling:
1 pint blueberries (about 0.6 pounds, 280g) 3 tablespoons sugar 1/4 teaspoon cinnamon 1 teaspoon lemon zest 2 teaspoons lemon juice 2 tablespoons cornstarch, flour, or minute tapioca
Egg wash:
1 egg white 1 teaspoon milk or cream
Add the butter and toss to coat with the flour. Using your (clean) hands, work the butter into the flour until the mixture resembles a coarse meal. Add the sour cream and mix with a fork until well incorporated. Knead with your hands until the mixture comes together as a ball. Divide into 3 equal sized balls of dough (it helps to use a kitchen scale). Form the balls into rectangular discs. Sprinkle with a little flour and wrap individually with plastic wrap. Chill for 1 to 2 hours or overnight (can freeze this point if making several days ahead). In a separate smaller bowl, put the blueberries, sugar, cinnamon, lemon zest, lemon juice, and cornstarch (or flour or minute tapioca), and toss to combine. Remove two dough discs from the refrigerator and let sit for 10 minutes to soften a bit. On a clean, lightly floured surface, roll out one disk to 11- x 17-inches and arrange on half of the sheet pan, with an inch of edge over the sides of the sheet pan. Roll out the second disc and cover the other half of the sheet pan. Fold the dough over along the edges and crimp. Remove any excess dough from center. Form into a ball, then use your hands to roll into a long rope. Crimp that rope of dough and form a rectangle in one corner of the sheet pan. This is where your berries and stars will go. The dough will help keep the blueberries from running into the strawberries. (If you don’t have excess dough at this point, no worries, you will later when you cut away the stars and stripes.) Put in the refrigerator to chill. Use a dinner knife (blunt) or a pizza wheel to cut out stripes. You’ll need 2 stripes that are about 18 inches long and 1 1/2 inches wide, and 2 stripes that are about 10 inches long and 1 1/2 inches wide. Use a star shaped cookie cutter to cut out stars. Place stars and stripes on a cookie sheet, sheet pan, or large plate. Brush with egg wash. Chill. Arrange the stars and strips of dough on top of the berries to form the flag. Chill for 10-15 minutes before baking. Remove from oven and let cool at least an hour before serving.
