Begin by frying the chicken breasts on both sides in the oil. Remove from the pan and set aside, then slice when cool.
In the same pan, add the butter. Allow to foam and toast ever so slightly, then add the garlic cloves and cook for a minute. Add the flour and mix in with a spoon, making sure the flour has no lumps. Add the milk in stages, ending up with a smooth sauce. Bring to the bubble and add parsley, parmesan and salt. Bring off the heat and pour over the pasta and chicken in a deep sided dish.
In a separate bowl mix together breadcrumbs, parmesan and parsley with the oil and sprinkle over the dish. Bake for half an hour.