For the chocolate mousse, mix the melted chocolate with the whipped cream in a bowl and place in the fridge for 10-15 minutes to set.
For the caramelised bananas, place the sugar, butter and vanilla pod into a frying pan over a medium heat. Cook until the butter has melted and sugar has dissolved, then add the lemon juice and banana slices and stir gently in the sauce to coat completely.
To serve, use two spoons to scoop three quenelles of chocolate mousse onto a serving plate. Add bananas and pour over any remaining hot toffee sauce.