Weigh about 1 pound of sweet potatoes, then peel them.

Wash the peeled sweet potatoes under running water.

Thoroughly dry the sweet potatoes with a kitchen towel.

Cut the sweet potatoes into irregular, bite-sized chunks.

In a large pan, heat about 6 cups of cooking oil to 340-350°F (170-177°C).

Carefully add the sweet potato chunks to the hot oil and fry for about 4 minutes until they are cooked through and lightly golden.

Remove the sweet potatoes from the oil and set them aside in a strainer to drain. Let the oil heat up again.

Fry the sweet potatoes a second time for about 2 more minutes until they are golden brown and crispy on the outside.

Remove the double-fried sweet potatoes from the oil and let them drain completely in the strainer.

In a separate, clean pan, add 2 tablespoons of cooking oil and 1/3 cup of sugar. Turn the heat to medium.

Heat the sugar and oil without stirring, only swirling the pan occasionally, until the sugar melts and caramelizes into a golden-brown syrup.

Once the syrup is ready, turn off the heat. Add the fried sweet potatoes and a sprinkle of black sesame seeds to the pan.

Quickly toss the sweet potatoes to coat them evenly in the hot syrup.

Immediately transfer the coated sweet potatoes to a parchment-lined baking sheet. Spread them out to prevent them from sticking together as they cool.

Let the Mattang cool down until the candy coating is hard and crunchy, then serve and enjoy.