Preheat the oven to 180°C (350°F) gas mark 4.

Coat the cake tins with nonstick spray and line the bottom with parchment paper. (See Note 1).

In a medium bowl whisk the flour, baking soda, and salt.

Using an electric whisk, beat the sugar, butter, and brown sugar in a large bowl until light and fluffy, for about 3 minutes.

Add the vanilla extract and the eggs one at a time, beating to blend between additions and occasionally scraping down sides and bottom of bowl.

Add dry ingredients and beat on low speed just to blend.

Add the bananas and sour cream and gently beat just to blend.

Fold in the mini chocolate chips.

Divide batter evenly among both tins.

Bake the cakes for about 35 minutes in the preheated oven.

Transfer the cakes to wire racks and let the cakes cool down for 10 minutes.

Invert the cakes onto the racks and peel off the parchment paper and let cool completely.

Using an electric whisk, beat the peanut butter, icing sugar, butter, vanilla extract in a medium bowl for 2-3 minutes, until a light and fluffy frosting forms.

Place 1 cake on a platter and spread part of the frosting over. Place the second cake on top.

Cover the top and sides of the cake with the remaining frosting.

Garnish with chocolate chips.

Cover and chill. Let stand at room temperature for 1 hour before serving.