Fries are best double cooked, that's why frozen fries are just as good as restaurant fries and better than home cooked. They flash fry them and freeze them, then you cook them again to crisp them up.
THE BEST fries are
triple cooked.
French cut potatoes and place them in a large pot with diluted vinegar to cover (you can pick what concentration you prefer, but something around 1-2% is a good starting point).
When your pot-o-acid is full of fries, put it on the stove on high heat and bring it to a boil.
This is the first cook.
Strain and set aside to cool.
Parfry according to your prefered "double fry" method.
This is the second cook.
At this point you can portion into freezer bags and store them for later.
The freezing tends to change the final texture of the interior.
Many people consider it an improvement.
When ready to serve do the second fry to desired color according to your preferred "double fry" method.
This is the third cook.
The first cook by boiling in acid chemically modifies the surface glycoproteins in the potato causing it to crisp up differently during frying. It is possible to over-do this, both in acid concentration, duration of exposure. Figure out what works for your preferences, equipment, and conditions.
You do not have to use plain-jane distilled white vinegar, but since that's a major flavor in tomato ketchup, it's expected and well-paired. Malt vinegar is also really really good if you've ever found yourself nostalgic for proper fish-n-chips, but does introduce wheat allergens people don't expect in french fries. My enthusiasm for further experimentation had faded by this point.
Note: it's probably not good for the stability of your oil.
At least that's the explanation I have for why more places don't do this.
Enjoy the additional carcinogens. Adds flavor. Tasty!
