Make Potato Noodles:

1. Peel and chop the potatoes into small cubes.
2. Add potato to a pot of water. Bring it to a boil and cook until soft and fork-tender. 
3. Drain and transfer the cooked potatoes to a big bowl. Use a fork or potato smasher and mash the potatoes until smooth and no lumps.
4. Add the potato starch to the mashed potatoes. Add water gradually (little at a time) and use your hands to mix. Keep kneading until it forms a smooth, pliable dough. Add more water if the dough is too dry, and add more potato starch if the dough is too wet. 
5. Take about 1 inch dough, roll into a ball, then press halfway down with a clean wine bottle to create a mushroom shape. Repeat with the remaining dough.
6. Bring a pot of water to a oil, add potato noodles in batches, then cook for a few minutes until they float to the top and become bouncy.
7. Transfer the potato noodles to a serving plate or bowl. Add the chili sauce, then drizzle hot oil on top.
8. Toss the potato noodles with chili oil, then garnish with chopped green onions. Serve hot and enjoy!

Make Chili Oil:

1. In a bowl, combine soy sauce, black vinegar, Chinese chili flakes, chili powder, garlic, and green onion together.
2. In a small saucepan, add 2 tbsp of neutral oil and heat over medium heat. Oil should be ready when you start seeing small bubbles. You can also test the heat by submerging a wooden chopstick in the oil and it should start to sizzle. Carefully pour the hot oil over the chili sauce mixture when ready to serve. Taste and add more seasoning if desired.

For more detailed instructions on how to make chili oil, visit this blog post.