Combine first three ingredients, rub in the clarified butter and then knead into a stiff dough with cold water and leave to rest, covered for 1/2 an hour.
Roll into desired size rounds and prick with a fork all over the surface, to avoid puffing up while frying.
Heat oil until a piece dropped in its rises to the top at once.
Put in the mathies, turn once and continue to fry over medium heat till crisp.
Drain on an absorbent paper and serve.
Key Ingredients: water chestnut flour, potatoes, rock salt, clarified butter, water, vegetable oil