Preheat your oven to 190C/375F/Gas mark 5 and either line or lightly grease two 8inch round tins that are at least 2 inches deep and place to one side.
Cream the butter, sugar and peanut butter together until they are light and fluffy. About 2-3 minutes if you are using a stand or electric mixer.
Then add the eggs one at a time beating in-between each addition then add in the vanilla extract, mashed bananas and buttermilk. Mix until everything is well combined about another minute.
Sieve in the baking soda, baking powder, salt and flour.
Then gently fold in the dry ingredients into the batter.
Divide the batter equally between the two tins and gently spread it out in the tin so it is level. Then pop the tins in the middle of your oven.
After 25 minutes you need to reduce the temperature of your oven to 170C / 325F / Gas mark 3 and bake your cake for a further 10 minutes.
After this 10 minutes check you cake for doneness, it should just be starting to pull away from the sides of your tins be a light golden colour and be firm to the touch. If you have a pick press it into the middle and it should come out clean. If it doesn't pass these tests give your cake a further few minutes and test again.
Take the cakes out of the oven and let them rest in their tins for 5 minutes then transfer them to a wire rack to fully cool down.
Once the cakes are fully cooled down its time to make the frosting.
Using an electric mixer or stand mixer beat the butter until it is light and fluffy, this will be about 5-7 minutes.
Mix in the peanut butter and beat for another minute or two until it is well mixed into the butter.
Turn your mixer off and pour in half of the icing sugar, on a low speed start to mix it in. When its fully combined repeat with the remaining icing sugar.
Add in the cream cheese and beat on a medium speed for a minute until it is well mixed in.
Your cake is now ready to decorate.
Put half of your frosting on top of one of your cakes and gently spread it out over the sponge but keep it a few centimetres from the edges and then sandwich it together with the other half.
Then place the remaining frosting on the top of the cakes and gently work in over the top and down the side of the sponges until everything is fully covered.
If using sprinkle your peanut butter chips or chocolate chips over the top.
Slice and serve.
Kept in an airtight tin in cool temperatures this cake will last 4 days.