These simple brownies use sweet potatoes to bring some ... Grease and line the base and sides of a 23cm/9in loose-based square cake tin with baking parchment. Mix the flour, cocoa and bicarbonate ...

The chocolate sponge cake layers will freeze, unfilled, well-wrapped in clingfilm, for up to one month. Defrost at room temperature, unwrap and fill. This simple chocolate cake is best eaten on ...