With a cup, cut out circles from the laid out sheets of puff pastry. Cut the mozzarella into round slices. Put a piece of mozzarella on each puff pastry circle, sprinkle a little basil and cover with a second circle of puff pastry.
Gently pinch the ends together and arrange them in an oiled baking dish. Brush the tops with an egg beaten with a little water.
Put them to bake up to a nice tan in a moderately preheated oven.