Parboil potatoes 5 minutes in salted water. Let cool then cut into wedges or chunks and dress with oil in a roasting pan. Toss with whole, cracked garlic cloves and chopped rosemary, salt and pepper.
Preheat oven to 425F.
Using a cleaver, a large sharp kitchen knife or shears, split bird down the back, open and flatten it. Butterfly it then loosen the skin all over the bird, being careful not to tear it. Dress with EVOO, season with salt and pepper.
Heat EVOO, about 1 tablespoon, in a small skillet. Brown pancetta then combine with shallots, minced garlic and chili. Stir 2 minutes then transfer to bowl to cool. Stir in parsley, cheeses and nutmeg. Spread the cheese and parsley mixture all over the chicken under the skin in an even layer. Roast on a baking sheet covered loosely with foil for 30 minutes then uncovered an additional 30 minutes. Roast potatoes alongside the chicken for the last 15 minutes of cooking time.
Serve with a tomato-arugula salad alongside.