Preheat the oven to 180'C.
Peel the bananas and puree with half of the caster sugar. Sieve the flour with the baking powder.
Cream the butter and remaining sugar until smooth and creamy using a whisk attachment for your stand mixer. Add a spoon of the sieved flour to help the mixture to bind and then add one egg at a time until all incorporated.
When all the eggs have been added, use a spatula to gently fold in the flour. When all of of the flour is added fold in the banana puree.
Spoon or pipe the mixture into cupcake cases until 3/4 full and cook for 12 minutes.
Line a deep baking tray with greaseproof paper.
Scrape the seeds from the vanilla pod.
Place the butter, milk, vanilla, and the dark sugar into a saucepan and heat on a medium heat.
Boil the mixture for 2-3 minutes until the sugar has melted is a caramel consistency. Mix the toffee as it cooks so as it does not burn around the edge of the pan.
Remove from the heat and stir in the icing sugar. Pour teh mixture onto the lined tray and leave for 15 minutes to cool.
Once the toffee has set. Cut into small dice.
Scoop out a small piece from the top of the cake and fill with the toffee.
Set aside some toffee to sprinkle on top of the cupcakes.
Sieve the icing sugar.
Place the butter into the food mixer with a paddle attachment.
Beat the butter until light and fluffy. Slowly add the icing sugar until it is pale and soft. Remove the icing from the machine and place in a piping bag with a star nozzle.
Top the cake with the butter icing starting from the edge and working inwards. Finish with a few small chunks of the toffee.
«Use dried banana in the cake for a stronger flavour and a different texture.»