Boil the potatoes in their skins in salted water until they are soft.
Drain and let them cool down.
Peel off the skins and mash the potatoes in a bowl until they become a smooth pulp. Pass them through a sieve for the smoothest possible consistency. Avoid mixing too much to prevent the mixture from becoming gluey.
Add 1 teaspoon of salt and the cornstarch to the mashed potatoes.
Combine to form a thick, non-sticky dough.
Knead the dough a bit more on a floured work surface and shape it into a roll.
Divide the roll into 8 equal parts and roll each part into a smaller roll.
Cut each small roll into 12 pieces and form each piece into a ball.
Coat the rosette of a lemon juicer with some vegetable oil.
Press each potato ball as hard as possible onto the oiled rosette to form a bowl with internal ribs.
Repeat with all the potato balls.
Heat a generous amount of vegetable oil in a pot or deep pan over medium heat.
Fry the prepared potato crackers in the oil until they are puffed and golden.
Use a slotted spoon to remove the crackers from the oil and place them in a bowl lined with paper towels to drain excess oil.
Optionally, toss the crackers gently in a bowl with additional salt or serve them immediately with your favorite cold sauce.