Start cutting the mozzarella into 1 cm thick slices. Arrange them on a tray lined with paper towels and cover with other sheets of paper towels. ( If you use buffalo mozzarella before doing this step, leave it to drain in the refrigerator for at least a day ).
Gently press with your hands to pat the mozzarella and remove excess water. If necessary, change the sheets of kitchen paper until it is completely dry.
Then trim the slices of bread using a knife, in order to eliminate the external crust.
Lay the slices of bread on a cutting board, arrange the slices of mozzarella on top, so as to cover the entire surface, but without letting it out from the edges of the bread, salt and cover each slice with another slice of bread.
Press gently with your hands to compact everything. Continue like this for all the other slices of bread, until you also finish the mozzarella.
Cut the sandwich to give the shape you prefer.
Break the eggs in a bowl and beat them with a whisk for a few minutes.
Take two more bowls. Place the flour in one, and the breadcrumbs in the other.
Dredge each piece of the sandwich first in the flour, then dip in the egg, so as to cover them entirely.
Then place them on a plate for a few seconds, in order to remove excess egg and avoid lumps when you pass it in breadcrumbs
Coat the sandwiches with breadcrumbs pressing lightly with your hand.
Transfer the sandwiches to a cutting board and with the blade of a knife lightly press the edges and the surface in order to uniform the breading and have a more precise shape.
Continue like this for all the other pieces and transfer them on a tray lined with parchment paper.
I recommend making a double breading. Dip the sandwiches again in the egg, then in the plate to remove the excess one and lastly coat again in the breadcrumbs.
As previously done transfer the mozzarella sandwiches to a cutting board and with the blade of a knife make the bread uniform.
Pour the oil into a pan and bring it to the temperature of 170-180 ° at the maximum.
Fry the sandwiches a few pieces at a time for 1-2 minutes, turning them occasionally with a skimmer.
When they are crispy and golden-brown, drain them from the oil and transfer them into a tray lined with paper towels to remove excess oil.