Wash the mustard greens under running water to remove any dirt, and air-dry for 12 hours to remove excess moisture. Rub with ½ tbsp salt until the leaves begin to wither. Transfer to a sterilised jar, cover with boiling water, and let stand at room temperature for 7 to 14 days until the water turns yellowish green.
In a small mixing bowl, combine red curry paste, chopped grachai, and curry powder. Transfer half to a separate bowl, coat the chicken pieces, and marinate in the fridge for 1 hour.
Place the marinated chicken in a pot with the coconut milk. Bring to a simmer, reduce heat, and cook until chicken is tender. Remove chicken and set aside, reserving the coconut milk.
In another pot, heat vegetable oil on medium and add the other half of the curry mixture. Fry until fragrant, then add the reserved coconut milk and simmer until thick. Add chicken and season with fish sauce.
Deep-fry 80g of noodles until crisp for garnish. Boil salted water, loosen remaining noodles, and cook for 1–2 minutes until tender. Drain and toss with vegetable oil.
Divide cooked noodles between 4 bowls, top with chicken curry, and garnish with mustard greens, red onion, coriander, and a lime wedge.
