makes one open-faced pie, serves 6-8
For the pastry- This will make enough pastry for two open-faced pies; wrap and freeze half for another time.
2 cups all-purpose flour
1 teaspoon kosher salt
1 tablespoon sugar
1½ sticks butter, cold, cut into cubes
1½ teaspoons cider vinegar
generous dash of rhubarb bitters
¼ cup ice water
In a large bowl, whisk together the flour, salt and sugar. Using a pastry cutter, cut the butter into the dry ingredients until they form small pea-sized pieces. In a separate medium-sized bowl, whisk together the egg, cider vinegar, bitters, and ice water. Make a well in the center of the flour/butter mixture. Add the egg/liquid mixture to the well; toss together using your fingertips until the mixture forms a shaggy dough. Turn dough out onto a sheet of parchment paper. Divide the dough in half; wrap each portion of dough in plastic wrap and refrigerate for at least one hour before rolling out. (If not planning on using the second portion of dough in the next day or so, double wrap it in plastic and freeze for a future bake.) On a lightly floured sheet of parchment, roll out one portion of dough into a 10” x 15” rectangle or into a 12” circle. Refrigerate the dough while you prepare the filling.
For the filling-
4 cups sliced rhubarb (¼” thick) (make sure to rinse the stalks and remove the leaves)
⅓ cup granulated sugar
2 tablespoons dark brown sugar
pinch of kosher salt
3 tablespoons tapioca starch
zest and juice of one small orange
½ teaspoon vanilla
egg wash made from one egg whisked with 1 tablespoon of milk or cream
sanding sugar or sliced almonds for garnish
Pre-heat the oven to 425 degrees F. Place the sliced rhubarb in a large bowl. In a medium bowl, whisk together the granulated sugar, brown sugar, salt, tapioca starch, and orange zest. Add the sugar/starch mixture to the sliced rhubarb; turn to coat using a rubber spatula. Add the orange juice and vanilla. Retrieve the dough from the fridge. Leaving a 1½” border, spoon the filling onto the center of the pastry, spreading it evenly with an offset spatula. Turn up the edges of the pastry, creating a ruffled edge all the way around. Brush the edge with egg wash and sprinkle with sanding sugar or with sliced almonds. Slide the pie (still on the parchment) onto a baking sheet. Refrigerate (or preferably freeze) for 20 minutes before baking on the middle rack of the pre-heated oven. Bake for 35-40 minutes, covering the pie with a sheet of parchment for the last 15 minutes to prevent over-browning. The rhubarb should be tender, the pastry golden brown. Set aside to cool before slicing. Any leftovers should be covered and refrigerated.