Cooked in the typical method -- fried in high heat in single batches -- fries can take 10 minutes or more to cook. The problem with this is that home fryers do not typically have the capacity to make large batches of french fries for a large number of guests. Moreover, cutting homemade fries can be time-consuming; getting this step out of the way ahead of time can save a lot of food preparation effort at mealtime.
The biggest problem with cutting fries ahead of time and leaving them in the fridge or on the counter for later is that the fries turn an unappetizing color of brown. While this will not make the most visually appealing finished product, the brown fries are still safe to eat and the taste will not be affected. However, if you want to pre-cut your potatoes and use them later -- while still maintaining an appetizing color -- place your cut potatoes in a bowl of water until you are ready to use them.
You can pre-cut potatoes and keep them long-term by freezing them. As with cut potatoes exposed to air, frozen potatoes can turn brown. To prevent this, blanch the potatoes by placing them in boiling water for one minute, and then immediately transfer them to ice water to cool down. Remove the completely cooled potatoes from the ice bath, blot dry with paper towels, and move potatoes to a freezer-proof bag and freeze.
Preparing Potatoes for Final Cooking
If frying pre-cut potatoes from a water bath, it is important to ensure that the potatoes are completely dry before dropping them into hot oil. Water on the surface of potatoes can cause hot oil to spatter and burn you. To dry them, simply set the potatoes on paper towels and blot them until all of their surfaces are completely dry.
If you are frying potatoes from a frozen state, it is not necessary to defrost or attempt dry them first. Simply drop the frozen potatoes directly into the hot oil to cook.
Make-Ahead the Belgian Way
If you are cooking french fries for a large party and have limited fryer space, use a cook-ahead process. Traditional Belgian-style french fries are cooked with a two-stage frying process. First, the cut potatoes are cooked for 5 to 7 minutes in 325-degree oil until cooked through but not brown. At this point the potatoes are mostly, if not all the way, cooked through. Next the fries are allowed to rest and cool outside of the oil for at least 30 minutes-- and up to one day. Finally, the fries are finished in 375 degree oil for two to three minutes, until browned, just before serving.