Preheat and Prepare: First things first, get your oven preheating to 220°C (200°C fan). Line a large baking tray with baking parchment. It’s important to use parchment, not foil, as it prevents sticking and helps the fries crisp up.

Peel and Cut: Wash and peel the sweet potatoes. Cut them into long, thin fries, about 1cm thick. Try to keep them as uniform in size as possible so they cook evenly.

The Soaking Step: Place the cut fries into a large bowl and cover them completely with cold water. Let them soak for at least 30 minutes (or up to an hour). This step is crucial as it draws out excess starch, which is a major contributor to soggy fries. This is a technique often used for regular potato chips, and you can learn more about the science behind it on sites like Serious Eats.

Dry Thoroughly: Drain the water from the fries and pat them completely dry with a clean tea towel or paper towels. I can't stress this enough – any remaining moisture will create steam in the oven and prevent them from crisping up. They must be bone dry.

Coat with Cornflour: Place the dry fries back into the (now dry) bowl. Sprinkle the cornflour over them and toss well until each fry has a very light, even coating. This thin layer is what will create that amazing crispy shell.

Season and Oil: Add the olive oil, smoked paprika, garlic powder, salt, and pepper to the bowl. Toss everything together again until the fries are evenly coated in the oil and spices. What works best for me is using my hands to really work the seasoning onto every fry.

Arrange on the Tray: Spread the seasoned fries onto the prepared baking tray in a single layer. Do not overcrowd the pan! If necessary, use two trays. Giving the fries space allows the hot air to circulate around them, which is essential for getting them crispy.

Bake to Perfection: Place the tray in the preheated oven and bake for 15-20 minutes. Then, carefully remove the tray, flip the fries over with a spatula, and return to the oven for another 10-15 minutes, or until they are golden brown and crispy on the edges.

Serve Immediately: For the best texture, serve these fries straight away. Garnish with a little finely chopped fresh parsley if you like. They are wonderful with a simple aioli or a spicy ketchup.