Cut the bananas into thin slices.

Chop the hazelnuts roughly or use ground hazelnuts, whichever you prefer.
Melt the chocolate in a double boiler or in the microwave and stir until smooth.
Filling:

Spread some melted chocolate on the puff pastry pieces.
Place a few banana slices on top.
Sprinkle some of the hazelnuts on top.
Rolling and sealing: Carefully roll the puff pastry pieces into small pockets or rolls. Press the edges well so that the filling does not leak out.

Brush with egg: Whisk the egg and brush the puff pastry rolls with it to give them a golden brown color.

Baking: Bake the puff pastry rolls for about 15-20 minutes until they are nice and golden brown and crispy.

Serving: Let the puff pastry rolls cool briefly and dust with powdered sugar if desired.

Enjoy these delicious puff pastry rolls as a snack, dessert or for a cozy afternoon tea!