Crispy baked oven fries with homemade ketchup

Oven fries are potato sticks tossed in a little olive oil and baked on a hot sheet pan until they are golden and crisp outside and fluffy inside. They get close to deep-fried fries with a fraction of the oil and none of the pot of hot fat, and they come out well once three things are right: the potatoes are cut evenly, their surface starch is rinsed off and they are bone dry before they go in, and they have room on the pan. A quick homemade ketchup, simmered from tomato puree while the potatoes soak, goes alongside.

Why the potatoes are soaked, rinsed and dried

Cutting a potato breaks open cells on every cut face and releases starch. Left on the surface, that starch makes the fries stick together and to the parchment, and it browns in patches before the inside is cooked. Thirty minutes in cold water draws it off: you will see the water turn cloudy. If you are short of time, rinse the cut sticks in a colander under cold running water until it runs clear. It is not quite as thorough, but it helps.

Then comes the step that matters most: drying. Spread the potatoes on clean kitchen towels and pat them dry on every side. Water on the surface has to boil off before browning can start, so wet fries spend their first minutes in the oven steaming, and they come out pale and limp. Dry fries start crisping almost at once.

Cut them evenly

Fries of different sizes cook at different speeds, so a mixed pan ends up with some burnt and some underdone. Cut each potato lengthwise into slabs about 3/8 inch thick, stack a few slabs, and cut them into sticks of the same width. Leave the skins on: they add flavor and crisp well, and they save time. Scrub the potatoes well first and cut away any green patches or sprouts, which taste bitter.

Oven heat and pan setup

A hot oven, 425°F (220°C), crisps the outside before the inside dries out. The pan setup is just as important as the temperature:

• Two baking sheets, not one. Two pounds of potatoes crowded onto a single sheet trap their own steam. Spread them over two sheets with a little space around each fry.
• Parchment paper. It keeps the fries from sticking without extra oil. A bare, lightly oiled pan browns them slightly more, but more of them stick.
• Racks in the upper and lower thirds. Swapping the sheets when you turn the fries evens out the hot spots that most home ovens have.
• Oil, lightly. Two tablespoons is enough to coat this amount. Toss the fries in a bowl so every side gets a thin film, rather than drizzling oil over them on the pan.

Turning once, at the right moment

Leave the fries alone for the first 20 minutes. In that time the undersides form a golden crust and release from the parchment on their own. Turn them too early and that crust tears off and stays on the paper. After the turn and the swap, they need 10 to 15 minutes more, until they are deep golden and a knife slides easily into the thickest one. Thinner fries finish sooner, so check the pan a few minutes early the first time you make them.

Choosing the oven temperature

The card uses 425°F (220°C) because at that heat the outside of a 3/8-inch fry turns golden in about the time the inside takes to turn fluffy. You will find recipes that bake anywhere from a moderate oven to a very hot one, and the trade-off is always the same:

Whatever the setting, wait until the oven is fully preheated before the fries go in; a cold start steams them.

Other methods you will see, and what they change

• Cornstarch dusting. Tossing the dried fries with about 1 tablespoon of cornstarch before the oil gives a thin, extra-crisp shell. Dust it on evenly and shake off the excess, or it leaves pale, chalky patches.
• Parboiling instead of soaking. Some recipes simmer the cut fries, starting in cold water, until a knife meets only slight resistance, then drain them and let them steam dry. The interior turns fluffier and the edges rougher and crunchier, but the fries are fragile and break easily when you spread them out. It also adds a pot to wash.
• Baking soda in the parboiling water. A small pinch makes the surface of the potato break down slightly more, which gives a craggier crust. Too much leaves a soapy taste.
• Hot water instead of cold. Some recipes soak the fries in hot tap water for a shorter time. Either way the point is to rinse off surface starch; the cold soak on the card is simply the more forgiving one.
• Oil heated on the pan first. Heating the oil on a bare sheet before adding the fries starts the crust faster, but the fries stick more, and hot oil spatters. Parchment is easier.
• No oil at all. Fries baked dry brown poorly and turn tough and leathery. The 2 tablespoons on the card is a thin film over two pounds of potatoes and is what lets them crisp.
• Air fryer. The same cut, soak and dry steps work. Cook in small batches in a single layer, shaking the basket once or twice, because a full basket steams the same way a crowded sheet does.
• Store-bought frozen fries. These are usually pre-cooked before freezing and are made to bake straight from frozen; follow the package directions rather than this method.

Getting ahead

You can cut the potatoes the day before and keep them covered with cold water in the refrigerator; that doubles as the soak. Drain and dry them thoroughly before oiling. The ketchup can also be made a day or two ahead and kept refrigerated.

The homemade ketchup

Ketchup is essentially tomato cooked down with vinegar, sugar and spices. Here, unsalted tomato puree is simmered with apple cider vinegar, maple syrup, onion powder, garlic powder, smoked paprika and salt for 15 to 20 minutes, until it has reduced to about half and is thick enough to hold its shape on a spoon. It splutters as it thickens, so lower the heat and stir more often toward the end. It firms up further as it cools, which is why it is made first, while the potatoes soak.

Taste it once it is cool and adjust: more vinegar for tang, more maple syrup for sweetness, a pinch of cayenne for heat. Maple syrup can be swapped for brown sugar, or for another liquid sweetener such as agave syrup, in the same amount; each changes the flavor slightly, and the guide to natural sweeteners explains how they differ. Without any sweetener it becomes a sharp, tomato-sauce-like dip rather than a ketchup.

Variations

Sweet potato fries

Sweet potatoes make good oven fries with a few changes. Cut them the same way; there is no need to soak them, but dry them if you rinse them. They contain more sugar than russets, so they brown faster and can scorch at the tips, and their moist flesh stays soft rather than turning crunchy. Bake them on the same setup and start checking a few minutes before the russet times. Some cooks toss them with a spoonful of cornstarch along with the oil for a drier, crisper surface.

Other potatoes and seasonings

• Yukon Gold potatoes give a creamier, denser fry. Waxy red potatoes stay firm and crisp less.
• Wedges: cut each potato lengthwise into eighths. Thicker pieces take longer; turn them when the cut sides are golden.
• Seasoning: swap the garlic powder for smoked paprika, a little chili powder, or chopped rosemary added for the last few minutes of baking so it does not burn.

Why not yuca fries

Yuca (cassava) fries are a popular alternative to potato fries. Food Standards Australia New Zealand explains that cassava contains cyanogenic glycosides, which can release hydrogen cyanide, that cassava sold there must be labeled to say it must be fully peeled and cooked, and that cooking methods such as boiling, steaming, baking or frying remove between 10 and 75% of them, none reliably enough on its own. Because a home recipe cannot guarantee that, this recipe uses potatoes.

Common mistakes and how to fix them

• Soggy fries: the potatoes were wet or the pan was crowded. Dry them well and use two sheets.
• Fries stuck to the pan: they were turned too early, or the starch was not rinsed off. Wait for the full 20 minutes before turning.
• Burnt edges, raw centers: the fries were cut unevenly, or too thick for the time. Cut them to one size.
• Pale fries: the oven was not fully heated, or there was too little oil. Let the oven preheat completely and coat every fry.
• Bland fries: salt sticks best when the fries are oiled. Taste one hot from the oven and add a pinch more salt if you like.

Storing and reheating

Oven fries are best straight from the oven, but leftovers keep. Refrigerate fries and ketchup within 2 hours, in covered containers at 40°F or below. USDA’s Food Safety and Inspection Service gives 3 to 4 days in the refrigerator for leftovers; use the same limit for the homemade ketchup. Reheat the fries on a baking sheet in a hot oven until they sizzle and reach 165°F. Cooked fries can also be frozen; FSIS says frozen leftovers keep 3 to 4 months for best quality, though reheated frozen fries are softer than fresh ones.

Allergy and ingredient notes

As written, the recipe contains none of the common allergens: no tree nuts, peanuts, soy, wheat, sesame or coconut. Check the labels of the tomato puree and spices if you need to avoid an allergen that may be handled in the same facility.

Oven fries go with almost anything. Serve them beside a bowl of chickpea ratatouille, or with baked BBQ tofu in place of its cauliflower mash.