Chocolate cake with sweet potato frosting

Instructions

1. Preheat the oven to 180°C, fan 160°C, gas mark 4. Grease and line a 28cm x 18cm rectangular cake tin with baking paper.
2. Put the dates in a heatproof bowl, cover with hot water and set aside to soak for 30 minutes until softened. Drain then blitz in a food processor until smooth.
3. In a small bowl, blend the cocoa powder with 6 tbsp boiling water to form a smooth paste. Transfer to a large mixing bowl, add the spread and beat together until smooth. Add the date purée and continue to beat until combined. Add the eggs, one at a time, beating well after each addition. Sift the flour and baking powder into the bowl and gently fold until just combined. Finally, fold in the milk and vanilla extract.
4. Spoon the mixture into the prepared tin, level the top, and bake for 40-45 minutes, or until risen and firm to the touch – the cake should be just shrinking away from the sides of the tin. Cool in the tin for 10 minutes, then turn out onto a cooling rack to cool completely.
5. To make the frosting, heat the sweet potato and both types of chocolate in a pan set over a low heat, stirring continually until the chocolate has melted and the mixture is smooth and combined. Transfer to a food processor, add the orange zest and juice and blitz until smooth.
6. Spoon into a bowl and let cool to room temperature. Spread the frosting over the cake to decorate, then slice and serve.