Why It Works
- Cutting the sweet potatoes into 1/2-inch sticks increases the ratio of crisp surface area to soft interior.
- A cooked cornstarch slurry forms a thin, even coating that crisps in the oven without turning dark or dusty, mimicking the light crunch of a deep-fried fry.
- Adding a touch of baking soda to the batter raises its pH, helping the fries develop deep color and roasted flavor before the interiors overcook.
Sweet potato fries should be a bar-food dream: sweet, salty, crispy, and golden. Yet, more often than not, they’re soft, soggy, or weirdly leathery—the disappointing cousin to the real-deal potato french fry. Even the deep-fried versions you find at bars rarely deliver that true shattering crispness.
The reason for this is that sweet potatoes simply aren’t built like russets. A combination of factors—less starch, more sugar, and more water—makes it harder for them to develop a crunchy crust before the inside overcooks and turns limp. I wanted to find a way to make sweet potato fries that are not only truly crisp but also oven-ready, avoiding splattering oil and deep-fryer cleanup: just an easy, weeknight-friendly tray of fries that could rival a great bar version.
Serious Eats / Mateja Zvirotić Andrijanić
The Recipe Testing
My goal was to achieve restaurant-level crispness without ever heating a pot of oil. Determined to crack the code, I tested several techniques I found in other recipes, including tossing the fries in oil then cornstarch before baking; cornstarch first, then oil; straight cornstarch batters with no oil; and no starch at all. Each of these versions had the same issues: They browned unevenly, turned dusty or tough, and tasted more bitter than sweet. While the flavor wasn’t awful, the texture was all wrong.
The Secret to Crispy Sweet Potato Fries
That’s when I remembered a technique I learned from my former colleague Lan Lam of Cook’s Illustrated. She used a cooked cornstarch slurry to make impossibly crisp oven fries with white potatoes. Instead of tossing the sweet potatoes in dry starch, which can lead to a chalky coating, I mimic her technique and whisk cornstarch and water together, then cook the mixture briefly in the microwave until it forms a smooth, yogurt-like paste. This pregelatinized starch forms a thin, cohesive batter that clings evenly to the fries and crisps beautifully in the oven without becoming dusty or dark.
Just as important as the batter itself is how the fries hit the pan. Before adding the oil, I spray the baking sheet with cooking spray—this ensures the oil spreads into a perfectly even film across the surface instead of beading up. That thin, uniform layer of fat allows the fries to make consistent contact with the heat, crisping evenly rather than steaming or scorching in patches. In essence, it creates a shallow-frying effect in the oven.
Serious Eats / Mateja Zvirotić Andrijanić
Fine-Tuning the Texture
But creating a crisp outer texture wasn’t the only hurdle. Sweet potatoes cook quickly—too quickly, in fact. By the time they’re browned, they’re usually overdone inside. To speed up browning without extending the bake time, I add a pinch of baking soda to the batter. It raises the pH just enough to encourage the Maillard reaction, producing a deeper color and subtle roasted flavor before the interiors turn mushy.
For extra texture, I take a page from Marianne Williams’s air-fryer sweet potato fries: I whisk in white rice flour, which helps create a delicate, shattering exterior reminiscent of tempura. I tested this recipe with Bob’s Red Mill Stone Ground White Rice Flour. It is finely ground but still has a coarser texture than all-purpose flour or other starches and it holds its texture when baked on the sweet potato fries.
Finding the Perfect Cut
Cut size was another key factor. Thinner fries overcooked before crisping, while thicker ones stayed gummy inside. The sweet spot—literally and figuratively—was 1/2-inch-thick sticks, cut from halved sweet potatoes so they’re around 2 1/2 to 3 inches long. These dimensions give you the perfect contrast: golden, crackly outsides and creamy, custardy centers.
Serious Eats / Mateja Zvirotić Andrijanić
The Payoff
The result is fries that don’t wilt once they’re out of the oven—and are crisp enough to hear with every bite. Once they’re baked to perfection, I toss them in a homemade seasoned salt with paprika, garlic powder, and cayenne. Waiting to toss them in the salt until after baking means the spices stay vibrant-tasting and don’t burn and become bitter in the oven. Paired with a tangy, spicy fry sauce, these are the rare sweet potato fries that deliver on their promise: crispy, flavorful, and totally worth the oven time.
Serious Eats / Mateja Zvirotić Andrijanić
