Peel the onion, cut it in half and then into slices. In a pan, stew them with a little oil. Add salt and pepper to taste. Let them cool down.
Dice Fontina PDO removing the rind and keep it aside.
Coarsely chop the stale bread and transfer it to a bowl with the milk.
In another bowl, beat the eggs adding herbs, salt and pepper.
Add the bread, Fontina PDO and onions to the bowl and mix well.
In a pan with the lid on cook the omelette with a little oil over low heat.
Serve warm or lukewarm.