Soften the gelatine in cold water for 2 minutes.
Put the toffee sauce in a small saucepan over gentle heat and stir in the gelatine until it has dissolved.
Stir the toffee mixture into the crème fraîche and add the dried bananas, reserving a few for decoration.
Meanwhile, beat the egg whites until stiff, then fold through the toffee and banana mixture. Spoon into 4 glasses and decorate with the reserved banana chips and an extra dollop of toffee sauce, if you like.