Heat one tablespoon of olive oil in a skillet over a medium heat. Thinly slice the onion and add to the pan along with the balsamic vinegar and maple flavored syrup. Stir well to combine. Cook for 1-2 minutes until just tender then reduce the heat to low. Continue to cook for a further 5-6 minutes until the onions are sweet, soft and slightly caramelized.
Whilst the onions are cooking, heat the remaining olive oil in a separate skillet over a medium heat. Add the bacon and cook through until golden brown. Keep warm and set to one side.
Preheat a broiler to medium.
Divide the caramelized onions between the four pancakes.
Tear the bacon strips in half and arrange two halves on each pancake.
Roughly dice the Brie and arrange on top of the bacon.
Transfer the pancakes to a grill tray and broil for 3-4 minutes until completely hot through and the Brie has melted.
Finely chop the rosemary and sprinkle over the pancakes along with a generous pinch of black pepper to serve.