Mixture
Grate the onion and add it to a bowl with the ground beef. Also add the egg, salt, black pepper, garlic and mix well.
Grate the mozzarella cheese and set aside.
Place the seasoned ground beef over a sheet of parchment paper or plastic bag and spread it out very well, making it as flat as possible. Put the grated cheese all over the meat, evenly spread it again.
Roll this cheese stuffed meat, thoroughly pressing it down, into a log shape and take it to the freezer for 2 to 3 hours.
Into a bowl, add two eggs, a pinch of salt and the milk, mix very well. Add the wheat flour and mix again.
Take the meat out of the freezer and cut it into round slices, about 1-finger thick each.
Dip the meat slices in the mixture we've just set aside and fry them in hot oil, over low heat, for 7 minutes each side or until brown.
Serve.