Pour the chicken stock into a large saucepan and add the ginger, garlic, Thai fish sauce, lime leaves, star anise and chillies, bring to the boil, then turn down the heat and simmer for 20 minutes.
Put the vermicelli noodles in a heatproof bowl, pour over boiling water to cover and allow the noodles to sit for 5–10 minutes, or until as soft as you like them (I prefer mine to retain a bit of bite). Drain in a sieve or colander.
Spoon the drained noodles into serving bowls and add the slices of raw salmon, herbs, pineapple, pak choi and spring onions (scallions). Pour over the aromatic chicken stock and leave to stand for 5 minutes before serving, to lightly poach the salmon.