Cherry Peach Shortbread Cobbler

For the shortbread

Preheat oven to 400°f. Beat butter, brown sugar, salt and 2 1/4 cups flour at medium speed with a heavy-duty electric stand mixer just until combined. Place dough on a lightly floured surface; roll to 1/4-inch thickness. Cut rounds with a 2 1/2-inch fluted round cutter. Place rounds in a single layer on a baking sheet; cover and chill until ready to use. 

For the filling

Pulse ginger and turbinado sugar in a food processor 5 to 6 times or until well combined.  Pour into large bowl. Add lemon juice, peaches, cherries and remaining 3 tablespoons flour; toss to coat. Pour cobbler filling mixture into in a greased (with butter) 10-inch cast-iron skillet (or any other oven proof vessel) and pour any remaining juice over peaches.

Bake at 400° for 15 minutes. Remove from oven and place shortbread dough over peach and cherry filling. Brush rounds with egg white, and sprinkle with granulated sugar. Bake 17 to 20 minutes more or until golden brown.