Preheat oven to 220°C (425°F). Line two baking sheets with parchment paper or lightly grease them. Position oven racks so heat circulates (one in middle, one slightly below if using two).

Cut and dry sweet potatoes

Peel the sweet potatoes if you prefer (skins on are fine). Cut each into 1/3- to 1/2-inch thick fries: slice lengthwise into planks, then stack and slice into sticks. Put the cut fries into a large bowl of cold water and soak for 15–20 minutes to remove excess starch (this helps crisping). Drain and rinse, then spread on clean kitchen towels or paper towels and pat very dry.

Coat fries

In a large bowl, toss the dried fries with cornstarch until evenly coated. Drizzle with olive oil and toss to coat. Sprinkle smoked paprika, ground cumin, garlic powder, sea salt, black pepper, and optional cayenne over the fries and toss until evenly seasoned. Make sure fries are in a single layer when arranging on baking sheets—use two sheets to avoid crowding.

Bake

Arrange fries in a single layer on the prepared baking sheets with space between pieces. Bake for 12 minutes, then rotate sheets between racks and flip the fries. Bake another 10–15 minutes until edges are brown and crisp to your preference. If you want extra crispness, switch oven to broil for 1–2 minutes watching carefully to avoid burning.

Finish

Remove fries from oven, sprinkle with a pinch more salt if desired and chopped fresh parsley. Let rest 2–3 minutes to firm up before serving.

Vegan mayo

While the fries bake, make the mayo. In a small bowl combine vegan mayonnaise, lemon juice, maple syrup, smoked paprika, salt, and black pepper. Whisk until smooth and taste; adjust acidity or sweetness as desired by adding a little more lemon juice or syrup. Chill until ready to serve.