1. Cook the Potatoes: Steam or boil the peeled, cubed potatoes for 15–20 minutes until they are fork-tender. (Steaming is preferred to prevent them from absorbing too much water).

2. Mash Perfectly: While the potatoes are still hot, mash them in a large bowl until completely smooth. Use a ricer or fine mesh sieve if possible—any lumps will show in the noodles.

3. Make the Dough: Add the potato starch and salt to the mashed potatoes. Mix with a fork, then use your hands to knead it into a smooth, non-sticky dough. If it’s too dry and crumbly, add water 1 teaspoon at a time. If it’s too sticky, add a pinch more starch.

4. Shape the Noodles: Pinch off small pieces of dough (about the size of a walnut). Roll them into balls, then roll them into thick worm shapes or press a bottle opening into them to create little mushroom shapes.

5. Boil: Bring a large pot of water to a boil. Drop the noodles in. Boil for 3–4 minutes, or until they float to the surface. Let them cook for 1 extra minute after floating.

6. Make the Sauce: While noodles boil, place the minced garlic, chili flakes, and green onion in a heat-proof bowl. Heat the 2 tablespoons of oil in a small pan until smoking hot, then carefully pour it over the aromatics to sizzle (this releases the flavor).

7. Combine: Stir the soy sauce, vinegar, and sugar into the oil mixture.

8. Serve: Use a slotted spoon to transfer the cooked noodles directly into the bowl with the sauce. Toss well to coat. Serve immediately.