Peel and slice potatoes into 1/2-inch slices and then add the slices to a large pot. Cover the potato slices with water and bring the pot to boil. Once boiling, cook the potatoes for 8 minutes. Drain the potatoes and return them to the pot. 

Add parmesan cheese, egg yolk, chives, salt, and black pepper, and mash the potatoes until they are fully mashed and incorporated. 

Transfer the mashed potatoes to a sealed container and place them in the refrigerator for at least 1 hour to cool. 

Get two large bowls. Crack two eggs into the first one and whisk until the eggs are fully scrambled. In the second bowl add panko bread crumbs, salt, and ground black pepper and whisk to combine.

Create 8 to 10 patties about 3/4 inch thick from the mashed potato mixture. Dip each mashed potato patty first into the whisked egg and make sure there are no dry spots. Then move each one into the second bowl and ensure they are fully coated with seasoned bread crumbs. After they are all coated in bread crumbs, move each patty to a large plate or sheet pan to rest before frying.

Add neutral or vegetable oil one inch deep to a large skillet or pot over medium-high heat until the oil reaches 350 F (176 C). 

After the oil has reached temperature, fry each potato cake two or three at a time for 3 to 4 minutes or until the exterior is browned and crispy. 

Let the fried potato cakes cool on a cooling rack or paper towels while you fry the rest of the cakes. 

Eat while warm or store in the fridge for 2 to 3 days. Reheat in a 375-degree F oven for 10 minutes, flipping halfway.