Put 2 litres of chicken stock – or 1 litre of stock and 1 litre of water – in a big soup pot on the stove to boil, then turn down low to simmer until you’re ready to serve the soup. Season if needed with additional salt and perhaps some pepper.
While the stock is simmering, in a separate smaller pot, poach the chicken breasts in enough stock to cover the meat until just cooked, taking care not to over-do them. If you have a thermometer, do use it. Poke the biggest piece of chicken in the centre. You want it to register at least 70°C, aiming for a final internal resting temperature of 74°C. You want the meat to be white and soft, not brown and hard. When it's ready, remove the breasts and allow the chicken to cool a little before shredding it into bite-sized pieces, just by tearing it apart with your hands.
While the chicken is poaching, add the thick slices of carrot to the stock; when you do take the opportunity to skim off any fat that has floated to the surface of the stock and any impurities on the bottom.
Blanch the bean sprouts and Asian greens/lettuce and set both aside.
Boil the dried rice vermicelli noodles as per the instructions on the packet. Once they're ready, drain them, rinse them so they remain firm, and set aside.
While the noodles are boiling, finely chop your birds-eye chillies, chop your limes into quarters, wash and pat dry your fresh fragrant herbs, and put them into dishes on the table so your guests can garnish as they wish. I also like to provide additional bean sprouts and chillies.
Divide the noodles between the bowls – either two big bowls for two people or four smaller bowls for four – and place the Asian greens/lettuce on the noodles, then the carrots, and chicken.
Gently pour the stock on top, filling each bowl, then add the bean sprouts and sprinkle on some finely sliced spring onions.
Suggest to your guests that they squeeze a quarter of lime into their soup, garnish their noodles with more fresh fragrant herbs, perhaps sprinkle on some finely sliced chillies, and squeezes of sauces as they wish. Provide pepper, sugar, fish sauce, soy sauce, chilli sauce, chilli flakes, additional fresh chillies, and chilli oil.