Peel the potatoes and cut them into smaller pieces.
Place them in a pot with water and bring it to a boil.
Let them boil until the potatoes are so tender that they can be crushed with a wooden spoon, which takes about 15-20 minutes.
Drain the water from the potatoes and place them in a bowl with the butter.
Mash them together, e.g., with a fork or an electric mixer.
Place the bowl in the fridge to cool the potatoes.
When they are cold, they can be formed into balls of any size you prefer.
Place them in a dish and put them in the freezer until 15 minutes before serving.
The potato balls need to be breaded before frying to make them crispy. They can be fried crispy in the oven or a deep fryer at 190 degrees Celsius (374 degrees Fahrenheit).
Place flour in one bowl, beaten egg in another bowl, and bread crumbs/panko with salt and pepper in a third bowl.
First, roll the potato balls in the bowl with flour, then in the bowl with egg, and finally in the bowl with bread crumbs. They should be completely covered in bread crumbs.
Fry the croquettes for about 5-7 minutes in the hot oil or about 15 minutes at 200 degrees Celsius (392 degrees Fahrenheit) with convection.
Remove them from the deep fryer and let them drain on paper towels to absorb excess oil. Sprinkle salt on top, and they are ready to serve.