Begin by peeling and cubing the russet potatoes. Place them in a large pot of salted water and add a few cloves of garlic for flavor. Bring to a boil and cook for about 15 minutes, or until the potatoes are fork-tender.

In a mixing bowl, mash the drained potatoes until chunky. Add cream cheese, butter, and black pepper, then stir until smooth yet fluffy.

In two shallow dishes, prepare your egg wash by whisking together the egg and flour until smooth. In the second dish, pour breadcrumbs.

Using about ½ cup of the potato mixture, form it into a ball, create a small indentation, place a cube of mozzarella cheese inside, and seal it.

Heat oil in a deep pan to 350°F (175°C) for frying. Carefully place the coated cheese croquettes into the hot oil, frying for 2-3 minutes on each side until golden brown.

Use a slotted spoon to remove the cheese croquettes from the oil, letting excess oil drain off. Serve hot.