Preheat oven to 400°F. Line sheet pan with parchment paper.
In a small bowl, combine pistachios, honey, rosemary, salt and pepper.
Cut brie wheel into 16 cubes of equal size.
Place puff pastry on a lightly floured work surface, cut each sheet into 9 squares. Spoon about 1 teaspoon of pistachio mixture onto each square. Add brie cube. Carefully stretch and fold corners of pastry over brie, pinching firmly to close. (Making sure the pastry is tightly closed is very important and prevents the cheese from leaking.)
(You'll have 2 extra squares of puff pastry – a perfect use for any leftover pistachio filling.)
Place bites, seam down, on parchment-lined sheet pan. Brush pastry bites with beaten egg. Bake 15–20 minutes until golden and puffed.
Let cool slightly, then enjoy with a drizzle of hot honey or a dollop of fig or berry jam.
