Cook the eggs in boiling water for 5 minutes, or until semi hard-boiled. Cool under cold running water, then peel and set aside.
Cook the noodles according to the packet instructions, drain and leave in a bowl of cold water.
Peel and finely slice the ginger and prick the chillies, then add to a large pot with the stock, soy sauce, unpeeled garlic cloves, star anise and cloves.
Bring to a simmer, then switch off the heat and leave to infuse for 20 minutes.
Shred or very finely slice the runner beans on the diagonal, then very finely slice the carrots. Cook together in a pan of boiling water for 2 minutes, until tender. Drain, then plunge into cold water.
Strain the stock into a clean pot (discard the solids) and return to a medium heat. Slice the prawns lengthways, then add to the stock and cook until just heated through.
Trim and finely slice the radishes and spring onions. Toast the sesame seeds in a dry frying pan.
Drain the rice noodles and divide between 4 bowls. Sit the beans, carrot and prawns on top. Ladle over the broth and top with the radishes, spring onions, half an egg, toasted sesame seeds and a little chilli oil, if you like.