Put the 6 stemmed, seeded dried chillies in a heatproof bowl, cover them with hot water and soak for 10–15 minutes, until soft and pliable. Meanwhile, toast the 1 tbsp coriander seeds and 1 tsp cumin seeds in a dry pan over medium heat for 1–2 minutes, shaking often, until fragrant and only a shade darker, never deep brown. Tip them straight onto a plate to stop the cooking. While the chillies soak, roughly chop the 3 shallots, peel the 5 garlic cloves, slice the 20g ginger and 20g fresh turmeric, and cut the 800g chicken thighs into large bite-size pieces. Drain the chillies well once softened. That brief, watchful toast is what wakes the seeds' aromatic oils without the bitterness of scorched spice.

Add the drained chillies, shallots, garlic, ginger, turmeric (or 1½ tsp ground turmeric), toasted coriander and cumin, ½ tsp ground cardamom, 1 tbsp curry powder and 1 tsp shrimp paste, if using, to a blender or small food processor. Blend to a smooth, thick paste, scraping down the sides often and adding the 2–3 tbsp water only a spoonful at a time, just enough to keep the blades moving. The paste should hold its shape on a spoon, with no visible fibres or grit from the ginger and turmeric. If it does turn loose, expect to fry it a little longer in the next stage to drive off the extra water. That thick, smooth texture is what lets the paste fry properly and gives the finished broth a silky rather than gritty body.

Season the chicken pieces with the ½ tsp salt and ¼ tsp pepper and set aside. Heat the 2 tbsp neutral oil in a wide, heavy pot over medium heat, add all of the curry paste and fry for 2–3 minutes, stirring often, until very fragrant and slightly darker. Add about 200ml of the coconut milk, taking the thick cream from the top of the cans first, and keep frying and stirring for 3–5 minutes, until the mixture thickens and small beads of reddish oil separate at the edges. The paste should smell cooked and toasty, never sharp or raw. That oil separation is what gives the broth its genuinely deeper, rounder curry flavour, since the spices bloom fully in fat rather than steeping in liquid.

Add the seasoned chicken and stir to coat every piece in the fried paste, then cook for 2–3 minutes, until the surfaces turn opaque and begin to firm. Pour in the remaining 600ml coconut milk and the 500ml chicken stock, then stir in the 1 tbsp fish sauce, 1½ tsp palm sugar and 1 tbsp light soy sauce, adding the 1 tbsp Thai red curry paste now only if a deeper orange-red tone is wanted. Bring to a gentle simmer and cook, uncovered or partially covered, for 18–22 minutes, until the chicken is tender and reaches 74°C at the thickest piece. The broth should look golden, rich and lightly thickened but still pourable. That gentle simmer, never a hard boil, is what keeps the coconut milk from splitting harshly and the chicken from tightening.

While the curry simmers, set aside about 120g of the separated egg noodles for frying, keeping the remaining 480g for boiling. Pour neutral oil into a small, deep pan to a depth of about 4–5cm, no more than half full, and heat it to 170–175°C. Fry the noodles in small batches for 20–40 seconds each, until light golden, crisp and puffed in places, letting the oil return to temperature between batches. Lift them out onto paper towels to drain well. Meanwhile, bring a large pot of water to the boil for the remaining noodles. That fast, hot fry is what sets the noodles into a genuinely crunchy nest rather than a greasy, chewy tangle.

Once the chicken is cooked, taste the broth and adjust. Add more fish sauce, a little at a time, if it needs salt and savouriness, and a pinch more palm sugar if it tastes sharp rather than rounded. If the broth feels too thick, loosen it with a splash of extra stock or hot water; if it is too thin, simmer it uncovered for a few more minutes. Add salt only if it still needs it. The finished broth should be creamy but not heavy, warmly spiced, slightly sweet, salty and savoury, and rich enough to coat the noodles lightly. That final taste-led balance is what absorbs the natural variation in curry powder, fish sauce and coconut milk from brand to brand.

Drop the 480g noodles into the boiling water and cook for 1–2 minutes, just until tender but still slightly firm at the centre. Drain them immediately and rinse very briefly under cold water only if they seem to be carrying on cooking. If they look sticky, toss them with the 1 tsp neutral oil. Cook them only now, at the very end, since boiled noodles left waiting clump together and soften before the bowls are filled. That slightly firm drain is what keeps the noodles springy once they sit in the hot curry broth.

Divide the boiled noodles among 4 deep bowls, about 120g each. Ladle the hot curry broth and chicken over the top, making sure each bowl gets roughly 200g chicken and a generous share of broth. Pile the crisp fried noodles on top of each bowl and finish with cilantro leaves and lime wedges. If using the optional traditional garnishes, serve the 120g chopped pickled mustard greens, the thinly sliced shallot or red onion, and the chilli oil or flakes on the side, or add a little to each bowl. Serve at once. That last-minute topping is what keeps the fried noodles crisp against the soft noodles and creamy broth beneath.