1.Preheat oven to 180°C (160°C fan-forced). Grease two x 22cm-round sandwich cakepans, line bases with baking paper.
2.Sift flours, soda, cocoa and sugar into large bowl. Add butter, vinegar and milk, beat with electric mixer on low speed for 1 minute. Add eggs, banana and jam, increase speed to medium, beat 2 minutes. Divide mixture between pans.
3.Bake cakes about 30 minutes. Stand cakes in pans 5 minutes before turning top-side up, onto wire racks to cool.
4.Sandwich cakes with whipped cream, dust with sifted icing sugar.
You need 1 large overripe banana (230g), to get the amount of mashed banana required in this recipe This recipe is gluten-free and yeast-free The cake batter needs to be spread quite thinly to bake properly. If you haven’t got twox22cm sandwich pans use two x deep 22cm-round cake pans