Preheat oven to 160°C / 140°C fan assisted and line the bottom of 3x 20cm round cake tins with parchment paper, grease and flour the sides.
Whisk together flour with baking powder and salt in a medium sized bowl and set aside.
Then whisk together milk, mashed banana and vanilla in a large jug, set aside.
In a large bowl, cream the butter and sugars together with an electric mixer until pale and fluffy. Add the first egg and beat for about 1 minute, scrape down the sides of the bowl and add the second egg, beat again for 1 minute. Then finally, add the last egg and beat again for 2-3 minutes or until the mixture is very pale and creamy.
Add 1/3 of the dry ingredients to the butter mixture and beat just until combined. Add half of the wet ingredients and beat just until combined. Add ½ of the remaining dry ingredients, beating just until combined, then add the last of the wet ingredients and beat just until combined. Fold in the remaining dry ingredients.
Divide batter evenly between the prepared cake tins. Drizzle 125ml of caramel sauce into each pan and swirl into the batter with a knife. Tip: If caramel sauce is too thick to drizzle, warm it slightly in the microwave on a low power setting just until its a pourable consistency.
Bake for about 45minutes to 1 hour, or until a toothpick inserted in the middle comes out clean. Tip: If you’re baking all 3 cake tins in one oven, baking time will be about an hour, but less if you’re baking in two different ovens.
Once baked, leave to cool in the tins on wire racks before turning out. Leave to cool completely before assembling.
For the buttercream, combine butter, caramel sauce, vanilla and salt in a medium sized bowl and beat with an electric mixer until smooth. Add the icing sugar and beat on low speed to start, increasing speed as more of the sugar is mixed in, until the buttercream is smooth.
To assemble the cake, place one of the sponge layers on a serving plate (remember to peel away parchment paper). Spread 1/3 of the buttercream on top and repeat with a second layer of sponge and buttercream. Finally, place the last layer of sponge on top and spread with the remaining buttercream creating lovely swirls in the frosting. Just before serving, top off with sliced bananas, then drizzle with 125ml caramel sauce. And if you like, decorate with gold coloured sprinkles for that extra wow-factor.
*If using store-bought caramel sauce, we recommend buying delicious salted caramel sauce. They are usually sold in 260g jars and you will need 3 jars in total for this recipe.
Cake can be prepared the day before serving, simply prepare cake as above, but only go as far as layering the sponge with the buttercream. Store in an air tight container at room temperature. Then just before serving, top off with freshly sliced banana and caramel sauce.