Heat a pan with some salted boiling water. Break the block of noodles up into about 10 pieces. Add to the pan and cook for 4 minutes. Drain, run under a cold tap to cool and set aside.
Whilst the noodles are cooking, heat the oil in a large pan. Add the onions and pepper and cook for 3-4 minutes until soft.
Add the garlic and ginger and cook for 3 minutes.
Add the cabbage and cook for 1 minute. Add the stock and soy sauce and bring to the boil. Simmer for 4 minutes until the cabbage is tender. Add the cooked vegetables, noodles and prawns. Bring to a low simmer.
Add the lime juice and sesame oil and season to taste with the pepper. Ladle into bowls and serve.