Combine the chilies, garlic, ginger, 1 teaspoon salt, turmeric, and vegetable oil in a food processor or mortar and pestle and process into a fine paste. Set aside.
Place the potatoes in a saucepan with the water and bring to a boil over high heat.
Reduce the heat to low, cover the pan, and cook the potatoes until they’re soft and easily pierced with a fork, about 15 minutes. Reserve the cooking water.
Mash the potatoes while they’re still warm, using some of the cooking water to get a smooth consistency.
Mix in 1 tablespoon green chili paste, chickpea flour, 2½ teaspoons salt, 1 teaspoon turmeric, and mustard oil. Add enough reserved potato-cooking water as needed to make a soft dough. Taste the dough for heat level and seasoning.
Heat the cooking oil in a deep pan over medium-high heat.
Use a potato ricer (or sev machine) to press noodles into the oil.
Fry until golden brown and crisp, about two minutes.
Use a skimmer or slotted spoon to transfer the noodles to a paper towel-lined bowl.