Preheat oven to 350°F.

Spread the puff pastry sheet onto a counter and roll it out. Trim the pastry dough into a 10x10 square, reserving the leftover pastry dough.

Place the chopped pistachios in the middle of the puff pastry and top the nuts with the brie. Wrap the dough up and over the brie, starting at the corners. Invert onto a sheet pan lined with parchment.

Using a heart-shaped cookie cutter, cut a few hearts out of the reserved leftover pastry dough. 

In a small bowl, whip the egg with a little water to make an egg wash. Brush the top of the wrapped brie and place a heart or two on top.

Put into the oven and cook for 50 minutes or until golden brown.

Put the all the blueberries and strawberries, and half of the raspberries and blueberries into a medium-sized pot. Add sugar and lemon juice, and cook over medium-high heat until berries burst and the sauce thickens. Once the sauce has thickened, about 15 minutes, add in the Grand Marnier and the rest of the berries. Remove from heat and let cool.

Serve the warm brie en croute with four berry sauce alongside.