Preheat the barbecue to medium heat (375F - 400F). Score the brie with a sharp knife and rub 1 tsp balsamic vinegar on top and set aside on a plate
Once the barbecue is hot, add the cast iron pan to the grill and add the olive oil to the pan. Add the berries and 2 tsp balsamic vinegar and stir. Cook for 3-4 minutes to soften the berries.
Once the berries have softened and are starting to simmer, nestle the brie in beside the berries and close the grill. Cook for about 5-6 minutes more or until the brie cheese is starting to bubble. You can toast the bread slices on the grill too during this time if you'd like.
Once the brie is melted to your liking, drizzle over the maple syrup or honey over the brie and berries and then remove from the grill. Before serving top the brie with a few scoops of the berries and garnish with fresh basil. Serve with the toasted baguette or your cracker of your choice.
Notes
If you want to make crostini off the grill, preheat your oven to 400°Fahrenheit and slice a baguette into 1-inch thick slices. Brush the baguette slices with olive oil and place on a single layer on your baking sheet. Toast for 10 minutes, making sure to flip the slices halfway through. You could also use a sourdough baguette for this!
I highly recommend using fresh berries only for this recipe since they're all in season during the summer! Frozen berries hold a lot of water and can make this appetizer watery if used.