Peel the potatoes. Using a julienne slicer (or sharp knife), cut into very thin matchsticks about 1/8 inch thick. Keep them as even as possible so they cook at the same rate.

Place sliced potatoes in a bowl of cold water. Rinse several times until water runs mostly clear. This removes excess starch and keeps potatoes crisp. Soak 5 minutes, then drain and pat very dry.

Place a wok or large skillet over high heat. Add oil once the pan is hot.

Add potatoes to hot oil. Stir-fry on high heat for 3-4 minutes, tossing frequently. Cook until they soften slightly but still have a crisp bite.

Push potatoes to the sides of the pan, creating a pocket in the center. Add garlic and sliced chilies to the pocket. Stir for about 10 seconds until fragrant.

Add rice vinegar, sugar, and salt. Toss everything together for 30 seconds. Taste and adjust seasoning. Serve immediately.