Prepare the Potato Mixture: In a large mixing bowl, combine the boiled and mashed potatoes with 2 egg yolks. Mix well.

Add 1 teaspoon black pepper, 1 teaspoon paprika, and optional red pepper flakes if you prefer a spicy flavor. Stir in the grated cheddar cheese and 60 grams of softened butter until the mixture is smooth and well combined.

Form the Croquettes: Using your hands or a spoon, shape the potato mixture into small cylindrical or oval croquettes. Ensure that each croquette is uniform in size for even cooking.

Coat the Croquettes: Prepare three shallow dishes: one with flour, one with egg whites (lightly beaten), and one with breadcrumbs.

First, roll each croquette in the flour, ensuring it is fully coated.

Dip the floured croquette into the egg whites, allowing any excess to drip off.

Finally, coat the croquette with breadcrumbs, pressing lightly to ensure a good coating.

Fry the Croquettes: Heat vegetable oil in a deep pan or skillet over medium heat. The oil should be hot but not smoking.

Carefully place the croquettes in the hot oil, frying them in batches to avoid overcrowding. Fry for about 3-4 minutes on each side or until golden brown and crispy.

Remove the croquettes with a slotted spoon and drain on paper towels.

Serve: Serve the croquettes warm, ideally with a side of dipping sauce or a dollop of sour cream.