Heat the milk in a small sauce pot over medium heat, then add salt and a little bit of nutmeg, to taste. In another pot melt the butter and add the flour. Stir it gently and as soon as you see some flour foaming pour the mixture into the hot milk. Lower the heat and keep stirring until it becomes creamy.
Remove from the heat and set aside.
In a heavy-bottomed pan over medium heat, add the oil. When the oil is hot, add the onion and fry for 3 minutes, then add the pork and fry until it's partly cooked, approximately 5 to 6 minutes.
Remove the onion and pork from the pan to a plate and set aside to cool. Set up 3 dredging bowls.
Mix the bread crumbs and the Parmesan in 1 bowl, add the cold bechamel in another bowl, and the eggs beaten with salt and pepper, to taste, in the third bowl.
Using toothpicks spear a cube of pork, a cube of cheese and a piece of mortadella or ham onto each toothpick.
Roll the skewers first in the bread crumb mixture, then in the cold bechamel (with the help of a spoon), then in the beaten egg and finally coat again in the bread crumb mixture. Gently press the breading by hand to adhere the mixture. Reheat the oil and add the skewers (avoid turning too often, or the breading will break off). Once they become golden, about 5 minutes, gently remove them from the oil to paper towels to drain.
Transfer the "birds" to a serving platter and serve.
