Wash and boil the potatoes. Drain, peel, and mash them. Place the mashed potatoes in a large bowl, then add the beaten egg, salt, pepper, nutmeg, parsley, and grated cheeses.

Mix everything together. Meanwhile, cut the provolone into strips. Take a small portion of the potato mixture and flatten it to make a small indentation, then place a piece of provolone in the center.

Using your hands, shape the mixture around the cheese to form a cylinder-shaped croquette. Once all are formed, dip each croquette in beaten egg, then coat with breadcrumbs. Let them rest in the refrigerator for about 30 minutes. Fry in hot vegetable oil until golden brown. Drain the croquettes on paper towels when they're nicely crisp.