1 - Cut the mozzarella into 1 cm / o.4 inches slices. Crack the egg in a soup plate and beat it. Pour the flour and the breadcrumbs in two plates. Dip the mozzarella slices in flour.
2 - Cut the sliced bread in two and put one piece of mozzarella between the two halves, like a sandwich.
3 - Dip the sandwich in the beaten egg on both sides.
4 - Then coat the mozzarella sandwich with the breadcrumbs. Repeat the steps with the other sandwiches.
5 - Heat oil in a fry pan and fry a few sandwiches at a time over medium-high heat.
6 - Turn the sandwiches just once and brown on both sides. Drain them on paper towel and sprinkle with salt. Serve immediately.