Take out the puff pastry and leave on room temperature to defrost.
Open the pack of sausage and cut cross wise on both ends of the Sausage.
Cut the puff pastry in strips as big as both tips of Sausage can still see.
Wrap the puff pastry around the sausage and move to an oven with parchment paper.
Divide the egg yolk from the egg white only using the yolk.
Brush the yolk on top of the puff pastry and all around and sprinkle with grated Mozzarella cheese.
Put in a pre-heated 200 degree oven for around 15 minutes and serve with Tomato Ketchup.