This was another treat inspired by Dear Alton. He made it on his show, but we couldn't find the recipe. Ever up for improvisation, I made it up. I took one square of puff pastry and cut 1 inch strips off of each of the four sides. I stacked the strips back onto the edges of the piece I cut from to make walls, folding over the extra at the corners. In the space between the walls, I "docked" the pastry (poked several holes in it with a fork) to keep it from puffing there. I cut a second piece of puff pastry, just a little bigger than the first, to make a top.
Then I mixed just a little less than a pint of berries (blueberries and blackberries) with a few good handfuls of plain bread crumbs and sugar. I spooned the berries into the center of the square with walls and laid on the top, pinching slightly at the edges to keep it together. The whole thing went in a 400 degree oven for (roughly) 45 minutes--just pull it out when it looks good. I would recommend using parchment paper underneath. It still came off the pan even without it, but it was a bit of a struggle.
After letting it cool a bit, I decided it would be prettier if you could see the berries inside. So I cut an X in the top and folded each of the ensuing triangles back just a little at the tip to make the center. We didn't have whiped cream, but that would have been awesome. As it was, I dusted it with a little powdered sugar.