Step 1: Preheat your oven to 425°F (220°C). Line two large baking sheets with parchment paper. This is crucial as it helps prevent sticking and aids significantly in crispiness by allowing the hot air to circulate freely around each fry.
Step 2: Peel the sweet potatoes. Cut them into uniform fries, about 1/4 to 1/2 inch thick and 3-4 inches long. Uniformity is the golden rule for even cooking and achieving that coveted crispiness. If fries are of different sizes, some will burn while others remain undercooked.
Step 3: Place the cut sweet potato fries in a large bowl. Add the cornstarch and toss until every single fry is lightly and evenly coated. This is the cornerstone of our crispy oven baked sweet potato fries recipe, creating a protective, crispy shell.
Step 4: Drizzle the olive oil over the cornstarch-coated fries. Add the smoked paprika, garlic powder, onion powder, salt, and black pepper (and cayenne, if using). Toss vigorously with your hands or a large spoon until all the fries are thoroughly coated with oil and seasoning. Ensure no dry spots remain.
Step 5: Arrange the seasoned sweet potato fries in a single layer on the prepared baking sheets. This is arguably the most critical step for crispiness. Do NOT overcrowd the sheets; leaving space between each fry is vital. If they are too close, they will steam rather than roast, resulting in soggy fries. Use two sheets if necessary, even if it means running two batches.
Step 6: Bake for 15 minutes. After this time, carefully flip each fry using a thin spatula. This ensures even browning and crispiness on all sides. Also, rotate the baking sheets (switch racks if using two, and turn them front to back) for even cooking, as oven hot spots can occur.
Step 7: Continue baking for another 10-15 minutes, or until the fries are golden brown, deeply colored, and crispy to your liking. The exact time can vary depending on your oven and the thickness of your fries. Keep a close eye on them during the last few minutes, as they can go from perfectly done to burnt quickly. The goal is a perfect batch of crispy oven baked sweet potato fries recipe.
Step 8: Remove from the oven. If desired, garnish with fresh chopped parsley or a sprinkle of flaky sea salt for extra flair. Serve your perfectly crispy oven baked sweet potato fries immediately with your favorite dipping sauce. They lose crispiness as they cool.