Pre-heat your oven to 180C/gas mark 4.
In a large bowl, whisk together the eggs, sugar, meted butter until well combined and increased in volume.
Mash together the peanut butter and banana until you have a gloopy, sticky mixture. Stir this into the other wet ingredients.
Fold in the self raising flour and 75g of the chocolate chips.
Spoon the cake mix into a lined loaf tin and top with the last 25g of chocolate chips.
Bake in the centre of your oven for 1 hour or until the cake is cooked through - you can tell its done when the outside is golden brown, the cake is springy to the touch and a skewer comes out clean.
Leave to cool in the tin before turning out.