Transfer fries to a sieve and drain the water. Rinse once and then pat dry completely on a kitchen towel.

Put the potatoes in a medium sized bowl and toss with cornflour and ½ teaspoon salt. Shake off any excess cornflour.

Fill a pot with oil but leave enough room on the top for the oil to rise when you add potatoes or it will overflow. Heat the oil to 160°C (320°F). If you don't have a thermometer test with a chopstick. The oil will bubble slightly but won't be very hot.

On medium heat, drop the fries carefully in the pot. Don't overcrowd the pan. Fry in two batches. Let fries sit for 2 minutes and then stir gently so they don't stick together. Cook for total 5 minutes only.

Spread the fries on a wire rack. Let them cool down completely. It might take an hour or so. You can also pop them in the fridge or freezer to quicken the cooling process.

Heat the oil to 205°C (400°F) now. Check with a chopstick, there will be more bubbles this time.

The oil is very hot so carefully drop the fries into the pot. Fry in two batches and avoid overcrowding as that will bring the temperature down. Stir 2-3 times to attain an even golden colour. Fry for 5 minutes on high heat until they are golden brown. Keep an eye and don't burn.

Transfer to a sieve and immediately add the seasonings: a dash of extra salt, red chili powder, chaat masala and dried mango powder. Toss to season well.

Enjoy hot with ketchup or mayonnaise.