To make drunken cherries, add cherries, vanilla sugar and whiskey in a medium sauce pan over medium heat. Simmer until cherries have softened, released their juices and thicken slightly. Stirring occasionally for about 10 minutes. Set aside to cool.
Preheat oven to 400°F. Line a baking sheet with parchment paper.
Make an egg wash by beating 1 tbsp of water with the egg.
Place the thawed puff pastry sheet on the prepared baking sheet and place brie round in the middle of the puff pastry.
Fold one edge of the puff pastry dough on to the brie , leaving some of the top of the brie exposed. Brush the top of the puff pastry with egg wash, using a pastry brush. Fold up the opposite side then brush top dough with egg wash. Repeat with remaining edges until the brie is covered with the puff pastry, ensuring some of the top of the brie is exposed.
Sprinkle almonds on puff pastry and bake for 20-30 minutes until golden and brie has melted.
Remove from oven and plate. Top with drunken cherry sauce and garnish with fresh rosemary sprigs.
Serve hot with crostini and apples.