These fries are easily addictive. They are easy to make and the flavor is outstanding. Duck fat can be purchased at specialty stores like Williams Sonoma and Sur la Table. Smaller local markets also carry duck fat, however call before going to make sure it is in stock. The cooking time on these fries are dependent upon the size of them. If you prefer skinny thin fries, cook for a shorter amount of time. If you prefer fat thick fries, the cooking time may be longer.