Start by cutting the chicken breasts - slice each of them into 3 thin fillets.
Then cover them with plastic wrap and pound them very well to tenderize.
Season them with a pinch of salt, a pinch of black pepper and set aside.
Next, cut the sliced mozzarella cheese and the ham into small squares.
Transfer everything to a medium bowl, add the cream cheese, the oregano and mix everything very well until combined.
Now, take one of the fillets we prepared and place it in a ladle.
Add one tablespoon of the filling we prepared and close it by forming a little bundle.
Then, tie it with a piece of string.
Repeat this process with all the chicken and the filling.
Transfer these bundles to a large baking tray lined with parchment paper and brush melted butter over everything.
Take to a preheated oven at 350° F and bake for 30 minutes.
After this time has passed, remove the strings from the bundles.
Add the grated mozzarella cheese, divided between them.
Take the baking tray back to the preheated oven at 180° C (350° F) and bake until the cheese melts and browns.
Serve.