Slice off the top rind of the Brie, or score it in a criss-cross pattern with a sharp knife.
In a small bowl, stir together the cranberry sauce and balsamic vinegar.
Finely chop the leaves of 1 rosemary sprig and stir that in as well.
Place the Brie in a pie plate or shallow baking dish and top with the cranberry mixture. Sprinkle with pepper and add the other sprig of rosemary.
Bake for 10-15 minutes, or until it’s as oozy as you like it.