Place unpeeled potatoes in a large pot and cover with cold water. Generously season the water with salt and bring to a boil. Cook until potatoes are fork-tender, 25-35 minutes, depending on size.

Drain potatoes and cool slightly.  When cool enough to handle, peel the potatoes and pass through a ricer into a large mixing bowl. Alternatively, potatoes may be mashed with a potato masher. Note the texture may not be as smooth. 

Add egg yolk. Mix and add fresh parsley, parmesan, and cubed mozzarella. Mix well and shape into 8 oval croquettes. Arrange the croquettes on a small baking sheet lined with parchment paper. Place in the refrigerator for 30  minutes. 

In a medium saucepan, heat one inch of vegetable oil to 350˚F.

Prepare a breading station: In one shallow dish beat two eggs. Place breadcrumbs in a second shallow dish. 

Generously, season the eggs and the breadcrumbs with salt and pepper, to taste. 

Roll each croquette into the beaten eggs. Let excess egg drip off and then dredge in the breadcrumbs, pressing lightly so the breadcrumbs will stick to the croquettes. 

Fry the croquettes, a few at a time, in the hot oil until golden-brown and crisp on all sides, approximately 3-4 minutes. Do not crowd the oil. Allow oil to return to 350˚F before adding next batch of croquettes. 

Remove from oil as they are ready and place on paper towel.  

Serve immediately with desired dipping sauces. Enjoy!