Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
On a lightly floured surface, roll the puff pastry into a 10×10-inch square.
Place 3–4 berries in the center of each square. Add a tiny ¼ teaspoon of jam if desired.
Gather the corners of the pastry up and over the berries, pinching tightly to seal.
Place balls seam-side down on the baking sheet.
✧ Make sure they are completely sealed to prevent leaking!
Whisk the egg and water to make an egg wash.
Brush the tops and sides of each pastry ball generously.
Sprinkle with coarse sugar.
Bake for 15–20 minutes, or until puffed and deep golden brown.