Begin by peeling and cutting 500 grams of potatoes into equal-sized cubes. Bring a large pot of salted water to a boil, then add the potatoes and cook until fork-tender, about 15–20 minutes. Drain and let sit for a few minutes to remove excess moisture.

Transfer the drained potatoes to a large bowl and mash until completely smooth. Mix in ⅓ cup of grated Parmesan, ¼ teaspoon of black pepper, and 4 tablespoons of potato starch. Stir in chopped parsley to create a cohesive mixture.

Divide the mashed potato mixture into two portions and form into balls. Roll each ball out to about ½ inch thick and cut into strips.

In a large, deep pan, heat enough oil for frying to 350°F (175°C). Test the temperature by dropping in a small piece of potato; if it sizzles, the oil is ready.

Carefully lower the potato strips into the hot oil in small batches, frying for about 5–7 minutes until golden brown and crispy. Turn occasionally with a slotted spoon for even frying.

Once cooked, remove the fries from the oil and let them drain on a wire rack. Sprinkle with additional Parmesan and salt while hot. Serve immediately.