Take a peach and cut it in half. Remove pits. Place cut side down on the BBQ on medium heat until it begins to carmelise (about 3 – 4 minutes). Turn over and cook for another 1 – 2 minutes. Remove from BBQ to a plate or bowl. Sprinkle with brown sugar and cinnamon. Add a scoop of vanilla ice cream in the center and drizzle with Grand Marnier, if desired.