Peel the potatoes properly and cut into french fries shape. Dip the cut potatoes in cold water and then pat dry carefully with a towel. Fry the potatoes for 30 seconds in moderately hot oil and transfer on absorbent kitchen paper towel. Transfer the half fried fries on a tray and pat with a towel so as to absorb the oil. Now add the corn flour and mix well. Freeze the cornflour coated fries for 30 minutes and fry again in moderately hot oil until crisp and golden brown in colour. Once fried, transfer them on a tray and season with salt, coriander powder, chilli powder and chaat masala. Garnish with fresh parsley and black pepper and crispy and crunchy french fries are ready to eat!