- Grease two 8-inch round sandwich cake pans and line with baking paper.
- Sift flours, soda, cocoa and sugar into a large bowl and add butter, vinegar and milk.
- Beat with electric beater on low speed one minute.
- Add eggs, banana and jam and beat on medium speed for two minutes.
- Pour cake mix into prepared pans.
- Bake in moderate oven for 30 minutes or until cooked.
- Stand cakes in pans five minutes, turn onto wire rack to cool.
- Sandwich cakes together with whipped cream.