Preheat the oven to 180°C (160°C with fan) To make the sponge sieve the self raising flour and crush the bananas and the Carnation caramel with a fork. Beat the eggs and sugar with an electric beater until light and fluffy.
Fold the flour into the egg a third at a time until incorporated, then fold though the crushed banana and caramel.
Pour the sponge mix onto a lined baking sheet and bake for 10 minutes until browned and springy to the touch.
Sprinkle with a spoonful of caster sugar and tip onto a piece of parchment then roll tightly and leave to cool.
In the meanwhile whip the cream until stiff peaks form. Crush the second banana and fold through the cream.
To assemble unroll the sponge and spread a thin layer of Carnation caramel over the inner side. Then spread the creamed banana over the first third of the sponge as you reroll the sponge the cream will be pushed along to fill the whole roll. Drizzle the remaining.
Carnation caramel over the log and grate the chocolate to decorate.