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.