Dry-roast coriander and cardamom seeds, then coarsely crush with a mortar and pestle. Transfer to a food processor with garlic, shallots, chilli, ginger, turmeric, lemongrass, curry powder and 2-3 tbsp chilli soaking liquid, process to a smooth paste (add more liquid to loosen if necessary) and season to taste.
Heat oil in a saucepan over medium heat, add paste and cook, stirring, until thick and slightly darker in colour (3-4 minutes). Add coconut milk, stock and makrut lime leaves, bring to the simmer, then add chicken, reduce heat to low and simmer until tender (about 1 hour). Add fish and soy sauces, and sugar, season to taste, and keep warm.
Meanwhile, cook noodles in a saucepan of boiling salted water until tender (1-2 minutes), then drain. Divide among serving bowls, ladle in broth and chicken and serve garnished with a choice of toppings to taste.
