Late-Summer Mixed-Fruit Pie Recipe
3 medium plums, apricots, or nectarines
9 ounces pitted cherries
6 ounces fresh blueberries, blackberries, or raspberries
4 ounces Cape gooseberries, currants, or fresh cranberries
7 ounces sugar
1/2 teaspoon Diamond Crystal kosher salt; for table salt, use half as much by volume or use the same weight
1 1/2 ounces tapioca starch
Old-Fashioned Flaky Pie Dough, rolled and chilled as per the directions for a double crust
For the Egg Wash :
1 large egg
1 large egg yolk
1/2 ounce heavy cream
1/8 teaspoon Diamond Crystal kosher salt; for table salt, use half as much by volume or use the same weight
Wash plums , cut into 1/2-inch slices, and measure out 9 ounces in a large bowl. Add pitted cherries, blueberries, and Cape gooseberries, or whatever mix of fruit you prefer, to bring the total weight to 28 ounces . Toss with sugar, salt, and tapioca starch, folding with a flexible spatula until well combined. Scrape into prepared pie shell and top with remaining dough, as a solid sheet, a lattice, a herringbone, or checkerboard. Trim away excess dough and refrigerate to ensure top crust is completely chilled, about 30 minutes. Meanwhile, adjust oven rack to lower-middle position and preheat to 400 degrees F.
Whisk egg, egg yolk, cream, and salt in a small bowl. Brush over chilled top crust in a thin, even layer. This will give the crust a glossy, golden sheen, but is not necessary in any way. Place chilled pie on a parchment-lined rimmed baking sheet. Bake until crust is golden, about 1 hour, then loosely cover with tented foil. Continue baking until filling is bubbling even in the very center of the pie, about 15 minutes more. If crust completely covers filling, bake until pie reaches an internal temperature of 212 degrees F on a digital thermometer.
Cool pie until center of filling is no warmer than 85 degrees F on a digital thermometer, about 3 hours depending on the type of pie plate. Slice into wedges with a sharp knife, pressing firmly against bottom and sides of pie plate to ensure under-crust is completely cut. Wrapped in foil, leftovers will keep up to 3 days at room temperature; warm 10 minutes in a 350 degrees F oven to revive crust before serving.