Whisk whole eggs and 150grams caster sugar in an electric mixer until light and fluffy. Fold eggs through yoghurt in three batches. Whisk egg whites with 50grams caster sugar until soft peaks form, then fold through yoghurt. Churn and place in thefreezer. In a small saucepan, bring water to the boil with the remaining 50grams of sugar. Pour sugar syrup over chocolate and stir to melt chocolate. Stir through cream. Cut bananas in half lengthways, scoop on frozen yoghurt, drizzle with chocolate sauce and top with nuts.