Peel and chop Russet potatoes into chunks, then boil in salted water for 10-15 minutes until fork-tender. Drain and mash until smooth.

In a mixing bowl, combine warm mashed potatoes with a pinch of salt and potato starch. Gradually add warm water until smooth and slightly sticky.

Divide dough into 14 pieces and roll each into a ½-inch thick noodle, keeping them warm on a floured surface.

Boil a large pot of salted water and add shaped noodles, cooking for 2-3 minutes until they float, then cool in cold water.

Combine soy sauce, black vinegar, gochugaru, sugar, and salt in a bowl. Heat neutral oil until smoking and pour over the mixture.

Transfer cooled noodles to a mixing bowl, pour the chili oil sauce over, and toss well. Garnish with minced garlic and cilantro.