Peel and cut the sweet potato into strips. I tend to cut them into 1cm (1/3 inch) thick pieces. Place them in a cold bowl of water and let them sit for 45-60minutes.
Discard the water, give them a very quick rinse with cold water and pat them dry with a kitchen towel. Place them in a bowl and add 2 tsp of cornstarch. Gently mix them until they are evenly covered.
Place them on a baking tray that is lined with baking paper and make sure they touch each other as little as possible. Drizzle your fries with olive oil and season them with the spices.
Do NOT add any salt at this stage. If you do that it will turn the fries soggy. Add the salt after they are baked, just before you eat them.
Bake your fries in a preheated, fan assisted oven for a total of about 30-45 minutes at 200°C (390°F). The duration depends on how thickly you cut your fries.
Once the sweet potatoes started cooking and the oil is bubbling, open the oven door just a tiny bit. Just enough to let all the steam out that gathered in the oven at this point and close it quickly again. It should suffice to just open it for a few seconds, do not overdo it or the temperature will drop too much.
Turn the oven off once your fries are done and let them sit in the oven for another 5-10 minutes.
Just before serving season them with salt and serve them with whatever you prefer.