We are going on a skiing trip & are staying in a Condo. Can I precut potatoes &/or sweet potatoes into 1/4-inch matchstick fries before our trip then bake them there?
Regarding potatoes, not sweet potatoes:
It's actually great to precut potatoes for French fries, it gives you an opportunity to soak them in water, which removes the starch and simple sugars from the outside of the fries and even from just below the surface. In fact, many if not most places that make fresh cut French fries do cut the fries in advance and leave them soaking in the refrigerator until fried to order.
You don't say how long your drive is going to be, but if it is less than six hours, you can just put the cut fries and ice water in a Tupperware container for the trip. Longer than six hours you should probably either replenish the ice during the trip or use a cooler. Of course, depending on the weather, the trunk may work as a fridge - but don't let them freeze!
Your soaking container should either be pretty close to at least half-again the volume of your cut fries, or you should rinse them well first and change the water at least once while the fries are soaking.
From Caroline Russock writing for Serious Eats:
Russets or baking potatoes are the best, whereas waxy potatoes (such as Red Bliss or new potatoes) simply won't do. Soaking is key—this removes the starch, keeps the potatoes from sticking together, and eliminates the sugars that prevent the potatoes from achieving maximum crispness.
America's Test Kitchen (Sorry, paywalled) says pretty much exactly the same thing:
Experts agree (just ask McDonald's or our test cooks) that russet potatoes are the best variety for frying—either in a vat of bubbling oil or on a baking sheet in the oven. Unlike other potato varieties, russets produce fries with light, ethereal centers. But they are not perfect.
Russets can produce excessively thick crusts and somewhat dry interiors. The thick crust is caused by the browning of simple sugars in the russet, and the best way to remove some of the surface sugar is to soak the potatoes in water. The water has an added benefit. Potato starches gelatinize completely during cooking. The water introduced during soaking improves the creaminess and smoothness by working its way between the strands of gelatin starch. The final result is a fry that has a good surface crunch married to a smooth interior.
From the recipe attached the Serious Eats article:
Put the fries in a large bowl of cold water and refrigerate for at least 1 hour or up to 8 hours.
Be sure to dry them well before cooking!
Fresh cut French fries were a big part of the business in my café. It wasn't unusual for us to have French fries soaking for as long as two days, perhaps even three. I never noticed any quality problem from soaking too long, but the French fries were simply not good if we didn't have time to soak them for at least a half an hour.
Cook's Illustrated (also known as America's Test Kitchen) (Sorry, again paywalled) looked at oven fries. For that application, they soaked the cut potatoes in hot water. I suspect that starting at a higher temperature was beneficial for baking. To get the best of both worlds I might do a final soak in hot water. As I mentioned above, I haven't seen over-soaking as a problem.
For an easy, no-splatter oven fries recipe that would produce potatoes with a golden, crisp crust and a richly creamy interior, we followed this procedure: We soaked peeled russet potatoes, cut into wedges, in hot water for 10 minutes to remove starch. To prevent the potatoes from sticking, we poured oil, salt, and pepper on the baking sheet instead of on the potatoes. And to get the combination of creamy interior and crisp crust we wanted, we covered the potatoes with foil to steam them for the first five minutes of cooking for our oven fries recipe and then uncovered them and continued to bake until they were golden and crisp.
That doesn't sound like a good idea. A whole unpeeled potato or sweet potato requires no extra effort or care to keep it fresh and nice, but if you cut either of them up, you now need a container to keep the moisture in and the dirt out. Depending on how long before you cook it, you may even be entering into "food-safety" territory (especially if you ask the folks here). At the very least, the cut surfaces of the regular (non-sweet) potatoes will turn gray on the drive up to your condo.