Grease and flour two 8” round cake pans. Preheat the oven to 350 F.
In a bowl, whisk together the mashed banana, eggs, oil and sugars until well mixed. Add the peanut butter, salt, soda and vanilla and whisk well.
Whisk in the cocoa and flour until the mix is just combined. Divide the batter between the two prepared pans. Bake for about 35 minutes, until a cake tester comes out clean or you can press the top of the cake and it springs back.
Once the cake layers are cool, make the frosting:
Using a rubber spatula, press the cream cheese into the bowl over and over again to smooth it out. Add the butter and beat them together until just combined. Add the powdered sugar, vanilla, salt and peanut butter and beat until creamy.
Use a bread knife or cake leveler to slice the cakes in half lengthwise. To assemble:
Stack the first layer of cake (us a bottom layer) and spread a few tablespoons of frosting over it, adding halva crumbles if you are using. For the second, use a top layer but flip it so the inside of the cake is on top. Spread frosting, add halva.
For the third layer, add the top of the second cake, also flipped upside down. Spread frosting, add crumbles. The top layer will be the bottom layer of the other cake. Spread frosting, sprinkle on the crumbles.
Cake keeps for a few days, store in an airtight container. If you used halva, it’ll likely seep a bit but taste fine.