Cut the sweet
potato into 2cm (3/4 in) cubes. Place in a large saucepan and barely
cover with cold water. Bring to the boil, reduce heat and simmer for
about 10-12 minutes, or until potato is cooked through, but sill holds
it shape. Alternatively, microwave on 'high' for 5-6 minutes. Meanwhile,
slice banana and toss in lemon juice. Drain the cooked potato and allow
to cool. In a salad bowl place the potato, banana, spring onions
(shallots) and dressing and toss gently to combine.