I've only been to Sardinia, but I can highly recommend it, great nature and beaches, the food is hardy and pastoral, lots of goat cheese and heavy pasta dishes. One standout dish was Zuppa Gallurese, which is a stew/lasagna based on bread soaked in a rich broth and baked with tonnes of cheese. Their limoncello is also insanely good.
We did have the advantage of an italian friend who's from there and we rented a car to drive around the island which made things a lot smoother, so your mileage might vary, but check out some of the farm-restaurants and the old castles if you get there.