1. Preheat the oven to 160°C. Grease and line three round 8-inch cake tins.
2. To make the cake, beat together the eggs and sugar until light and fluffy. Next add the oil, milk, vinegar and a squeeze of lemon. Mix together the grated chocolate and coffee and then pour into the mixer. Whisk to combine.
3. Sift in the flour, cocoa powder and bicarbonate of soda and whisk until smooth.
4. Pour the batter into the tins and bake for 50 minutes or until a skewer inserted into the cake comes out clean.
5. Remove from the oven and allow the cakes to cool in the tin for 10 minutes. Run a knife around the edges of cakes to loosen them and invert onto a wire rack. Tip: a piece of bread on top of your cakes will keep them moist as they cool.
6. Once cooled completely, trim the cakes if the tops are domed and cut each cake in half so you have six sponges.
7. To make the peanut butter icing place the icing sugar, peanut butter, butter and vanilla in the bowl of a mixer.
8. Mix on medium-low speed until creamy.
9. Then add the cream and beat on high speed until the mixture is light and smooth.
10. To make the caramel glaze mix half of the brown sugar and half the butter and salt in a saucepan over medium-low heat. Cook while whisking gently for 5 to 7 minutes, until it gets thicker.
11. Then add the rest of the butter and sugar, making sure it’s all incorporated. Add the vanilla and cook another minute to thicken further. Turn off the heat, and leave to cool slightly.
12. To construct the cake, ice your first sponge with a thick layer of frosting. Top this with a layer of sliced banana and then the second sponge. Add another layer of frosting, more banana and the third sponge cake.
13. Then cover the entire cake with the rest of the peanut butter frosting. Use a palette knife to get a smooth edge around and on top of the cake.
14. Drizzle the cake with the caramel glaze and finish off with crumbs from your leftover chocolate sponge.