Set broiler on high. Prepare your sheet pan with parchment paper.
Cut the brie into half inch slices and crumble the blue cheese. Set aside in bowl.
Lay flat bread on sheet pan. Set the brie around the flat bread, 5 pieces per bread. Sprinkle half the blue cheese over the bread and add the grapes. Do the same thing with the 2nd piece of flat bread. Place under the broiler.
Cook for 2 minutes until everything is bubbling and starting to brown. Remove from oven and place each bread on a serving plate that is slightly larger than the flat bread. Let cool 2 minutes. * note keep an eye on the broiler. it may be done sooner than 2 min or need a bit more time. So check after 1 min.
. In small mixing bowl, add the greens, blackberries, balsamic and olive oil. Toss until mixed as a salad. Add a heaping pile of the salad on top of each flat bread and serve.