Peel the potatoes and julienne.
Dump the julienned potatoes in a bowl and cover with water. Let sit for 10 minutes to allow the potatoes to expel starch. Drain well.
Heat the cooking oils in a wok or frying pan.
Before the oil starts to smoke, fry the Sichuan peppercorns and chilies.
When the oil is smoking, add the garlic and chilies. Stir fry for about half a minute. Make sure to keep the contents of the wok or frying pan moving to avoid burning the garlic.
Pour in the soy sauce and stir in the sugar.
Pour in two tablespoons water. Stir.
Add the potatoes and stir fry until the potatoes are coated with oil and sauce.
Cover the wok or frying pan tightly for half a minute without turning down the heat.
Uncover the wok or frying pan, drizzle in the black vingear and stir the potatoes thoroughly.
Tip the contents of the wok into a serving plate.
Garnish the Sichuan stir fried potatoes with sliced chilies, scallions and sesame seeds.
Serve immediately.