Preheat oven to 400 degrees F.
Cut 4 "walls" of puff pastry by cutting approximately 1-inch wide strips along each side of a sheet of puff pastry. Set "walls" aside. Poke the remaining "floor" of puff pastry with a fork to provide an escape for steam.
Lightly apply the egg wash just inside the cut edges of the "floor". Stack "wall" pieces on top of "floor" piece placing the cut edge of the "walls" on the outside edge. Dab ends of "walls" with egg wash and fold long pieces over to form a square.
Cut a 7 by 7-inch square out of the second sheet of puff pastry. Fold it in half and cut vents for steam along the fold.
Shake bread or cake crumbs on drained cherries and let sit for 10 minutes. Spoon cherry mixture onto pastry "floor", using more than you may think necessary to compensate for the pastry puffing. Apply egg wash on "walls" avoiding the very edge.
Lay vented "top" piece on top. Brush with egg wash.
Bake in oven for 30 minutes. Reduce temperature to 350 degrees F and bake for another 30 minutes.
Recipe courtesy of Alton Brown