Sear the herbs in salted boiling water, then drain and cut them into pieces.
Stir-fry one garlic clove with a spoon of oil in a pan and add herbs, to dissipate their excess water. Let them cool down.
Preheat the oven at 180°C.
Cut frankfurters into rounds and mozzarella into dice and add them to the herbs. Add parmesan and salt, if necessary.
Cover a sheet pan with parchment paper and put puff pastry on it. Pour the herb mixture at the centre of it and close the pastry forming a strudel. Brush the beaten egg and spread sesame seed over the surface.
Bake the strudel in the hot oven for about 25 minutes, until its surface becomes golden.
Let it warm up and serve the savoury strudel in slices.