Step 1: Preheat your oven to 400°F (200°C). Line two large baking sheets with parchment paper.
Step 2: Peel the sweet potatoes and cut them into uniform sticks, about 1/4 to 1/3 inch thick and 3-4 inches long. Aim for consistency to ensure even cooking.
Step 3: Place the cut sweet potatoes in a large bowl and cover them with very cold water. Let them soak for at least 30 minutes (or up to 1 hour). This helps remove excess starch for crispier results.
Step 4: Drain the sweet potatoes thoroughly and pat them bone dry with paper towels or a clean kitchen towel. Any residual moisture will prevent crispiness.
Step 5: In a large bowl, toss the dried sweet potatoes with olive oil until every piece is lightly coated.
Step 6: Sprinkle the cornstarch, smoked paprika, garlic powder, salt, and black pepper over the sweet potatoes. Toss again until all fries are evenly coated with the seasoning and starch mixture.
Step 7: Arrange the seasoned sweet potato fries in a single layer on the prepared baking sheets. Do not overcrowd the pans, as this will cause steaming instead of roasting. Use two sheets if necessary.
Step 8: Bake for 15-20 minutes. Then, carefully flip each fry and continue baking for another 10-15 minutes, or until they are golden brown, caramelized, and perfectly crispy. Keep a close eye on them during the last few minutes to prevent burning.
Step 9: Remove from the oven, let cool for a minute or two (they crisp up further as they cool), and serve immediately with your favorite dipping sauce.