If you’re looking for "wow" at your Fourth of July party, this berry-filled slab pie is the way to go. It comes together in almost no time and is a perfect way to treat a large crowd. Don’t forget the whipped cream!
In the bowl of a stand mixer fitted with the paddle attachment, add all-purpose flour, sugar and salt. Turn mixer to low to combine.
Scatter the cold butter over the flour mixture. Turn mixer to medium-low and combine until the butter becomes the size of peas. Then stream in the ice-cold water, mixing just until the dough comes together. (Careful: do not overmix, butter pieces should still be visible for the flakiest crust!)
Use your hands to remove the dough from the bowl and knead gently to quickly form it into a disk. Put aside one quarter of the dough for the topping, and form both pieces into rounds. (Note: It helps to use a scale for this step.) Wrap in plastic wrap and place in the freezer for 30 minutes, or until cold and firm to the touch.
Preheat the oven to 350°F. Line the bottom of a 13 x 18-inch rimmed sheet pan with parchment paper. Set aside.
Remove the larger disc of dough from the refrigerator. Lightly flour your work surface. Use a rolling pin to evenly roll the dough to 14 x 18 inches and lay over the prepared pan. Fold the dough over along the edges to create an even crust (NOTE: reserve any scraps and add to remaining dough for the stars and stripes). Prick dough using a fork.
Blind-bake the base. Cover dough with parchment paper and fill with rice, beans or pie weights. Bake for 30–35 minutes, removing parchment and weights after 25 minutes. Bake until crust is lightly browned. Remove from oven and let cool while you prepare the fillings. Turn the oven up to 425°F.
Fillings
In a medium mixing bowl, add all the ingredients for the strawberry-raspberry filling. Use a spoon to toss and combine. Set aside.
In a small mixing bowl, bowl, add all the ingredients for the blueberry-blackberry filling. Use a spoon to toss and combine. Set aside.
Top Crust Decorations
Lightly flour your work surface once again and roll out the remaining round of dough to ¼ inch thick and 17 inches wide.
Use a pizza wheel (or very sharp knife) to cut out the stripes. You will need two strips that are 17 x 1 inch, and two strips that are 10 x 1 inch.
Use a star-shaped 1 inch cookie cutter to cut out 12 stars.
Use the remaining dough to roll a long rope of dough that’s 13 inches long. This will be the barrier for the stars section.
To Assemble
Use the rope of dough to create an 8 x 6-inch rectangle in the left-hand corner of the base. Crimp the dough a bit to create a barrier. Pour the blueberry-blackberry mixture into the small rectangle.
Evenly spread the strawberry-raspberry mixture into the section where the stripes will go. Arrange the stars and stripes of dough on top of the berries to form the flag.
Make the egg wash by whisking the egg and heavy cream together until loose. Brush the egg wash over the stars, stripes and crust. Sprinkle the entire pie with sparkling sugar.
Place the pie into the oven and bake for 40–45 minutes, or until the filling is bubbling and the crust is golden. (Note: if the crust begins to look too dark, tent the pie with aluminum foil.) Remove pie from oven and place on a baking rack to cool completely before serving.