Preheat your oven to 400°F (200°C).
Roll out the puff pastry on a floured surface.
Cut the pastry into squares or circles, about 3 inches wide.
Place a small spoonful of marinara sauce in the center of each cut piece.
Sprinkle a tablespoon of shredded mozzarella over the sauce, followed by your choice of toppings.
Fold the pastry over the filling to create pockets, and press to seal the edges.
Brush the tops with beaten egg for a golden finish.
Place the bites on a baking sheet lined with parchment paper and bake for 15-20 minutes.
Remove from the oven and let them cool for a few minutes before serving.