the flour, confectioners' sugar, and salt in a food processor
until just combined. Add the butter and process until the mixture resembles coarse bread crumbs
. Add the ice water gradually and process until the dough
holds together when pressed between two fingers. Form the dough into a disk, wrap it in plastic wrap
, and chill for 30 minutes.
Preheat the oven to 350 degrees F.
8 cups of a 12-count muffin pan and line the pockets with strips of parchment paper hanging over the edges. These will help you lift out the tarts.
On a lightly floured work surface, roll out the pastry dough until it is 1/8-inch thick. Cut out 8 pastry circles, and use them to line the muffin pan cups. Cut out 8 additional circles to serve as the tart
In a medium bowl, toss together the cherries, apples, cornstarch and sugar
, and spoon the mixture into the pastry
cups. Top the tarts with the pastry circles, and crimp the edges together with a fork. Cut a small vent in the top of each of the tarts, brush them evenly with the egg white, and bake until they are golden, about 35 to 40 minutes.