Rinse the poussin and put it in a large pot. Add about 1 litre of water - it should cover the bird well. Peel the onion, garlic and ginger, add these to the water (as whole). Heat it up, and when the soup is about to boil, using a mesh sieve, skim off the scum that accumulates on the surface (keep the liquid at a gentle simmer!).
When the surface of the soup is scum-free, add the carrots, stock cubes and bay leaf, then bring to the boil.
Turn down the heat, put a lid on and gently cook for 35-45 minutes.
Now add the peas, beans and the parsley (tied together with some string). Turn up the heat and cook for a further 5 minutes or so.
Remove the herbs and the onion, then cut the carrot into bite-sized pieces before serving.