Perfect fries aren't some secret guarded by a grill joint downtown. You need a pan, oil, potatoes, salt and heat - and one rule most people skip: the potatoes get fried twice.

The potato decides before the oil does

The best varieties are high in dry matter and low in sugar, such as Agria, Kennebec, Monalisa and Russet. They absorb less water, so the fries come out crispier. Cut them into even sticks, about half a centimetre to a centimetre thick and seven to fifteen centimetres long. Thinner ones fry faster and are crispier; thicker ones have a creamier inside.

Soak the cut potatoes in cold water for 15 to 30 minutes to draw out the excess starch. Then dry them thoroughly with paper towels - every drop of water in hot oil means spitting.

The double fry

Use enough oil to cover the potatoes completely. Olive oil is recommended because it handles high temperatures well, and at home it can be reused up to three times. The first fry is at 140 to 150 degrees Celsius for six to seven minutes - that's when the potato cooks through. The second is at 175 to 180 degrees for three minutes - that's when the golden, crunchy crust forms.

Salt them as soon as they come out, while they're still hot. Never cover them, or they'll go soft - and serve straight away. The most common mistakes: an overcrowded pan, oil that isn't hot enough, skipping the second fry, salting before frying, and fries left waiting on the table.

Professionals go a step further: they first boil the potatoes in salted water with vinegar, dry them, fry them at 130 degrees for two to three minutes, cool them and freeze them. Before serving - seven minutes at 180 degrees. A full day's work, but that's exactly why fries like that are the ones you remember.