Beat the butter and sugar together with an electric whisk until light and fluffy, then whisk in the eggs one at a time.
1 cup unsalted butter, 1 cup light brown sugar, 2 large eggs
Beat in the yoghurt, bananas and peanut butter, then stir in the flour little by little with a wooden spoon until totally mixed in. Finally, fold the chocolate chips through the batter.
1/2 cup Greek yogurt, 3 ripe bananas, 1/3 cup peanut butter, 1 cup chocolate chips
Divide the batter between the two greased tins, then bake for 35 to 40 minutes or until the cakes begin to pull away from the sides of the pan and a skewer poked into the centre comes out without raw batter on it. Let cool for a while, then turn out onto a wire rack to completely cool.
For the frosting
Whisk together the peanut butter, butter and vanilla, then whisk in the milk little by little.
Fold in about half the icing sugar and cocoa, then whisk until well combined. Whisk in the rest until the frosting is smooth and spreadable*.
1 1/2 cups icing sugar, ¼ cup unsweetened cocoa powder
When the cakes are completely cool, spread half of the frosting on the top of one, then place the other cake on top. Spread the rest of the frosting over the top of the cake, then decorate with peanuts (if using). Will keep in an airtight container for at least 4 days (possibly longer - never lasted that long!)
Sugar: This is the second, less sweet version of this recipe. The sugar is already reduced as of course there's more sweetness in the chocolate chips and frosting. But by all means experiment by reducing it further. Readers have reported good results from doing this.Storing: Store in an airtight container in a cool place for up to 4 days. If the weather is warm, cover loosely with aluminium foil and store in an airtight container in the fridge for up to a week.Freezing: This cake freezes well either before or after frosting. After cooling completely, wrap the layers well in plastic wrap and/or aluminium foil and store in big containers or freezer bags for up to 6 months. If freezing after frosting, freeze first uncovered for 4 hours in the freezer. Then wrap well and freeze in a freezer bag or container for up to 6 months.Frosting: Frosting recipe slightly adapted from this recipe on Food.com. Add more icing sugar if still too runny; add more milk if too thick.