Start by cutting the pork loin into 1-finger thick steaks.
Transfer them to a chopping board, cover them with plastic wrap and using a meat mallet, pound well until tender.
Season them with the salt and the black pepper, flip the steaks and season on the other side as well.
Cut the onion in half then into thin strips.
Grate the potatoes and transfer them to a bowl, cover them with cold water and let them soak for 5 minutes.
Grate the mozzarella and transfer to a bowl, add the natural plain yogurt, the mayonnaise and the mustard, mix all the ingredients very well.
Now, cover the bottom of an ovenproof dish with the grated and drained potatoes.
Top the potatoes with the onion strips, then add the pork steaks and the cheese mixture we made, spreading it out well.
Cover it all with foil, take to a preheated oven at 200°C (392°F) and bake for 20 minutes.
After this indicated time, remove the foil.
Take it back to the oven at 200°C (392°F) and bake for another 20 minutes.
Serve.