Recipe details

Method

1. Prick the sweet potato a few times with a fork, then microwave for 6 minutes until tender. Peel off the skin. Alternatively, peel the sweet potato first, cut into chunks, then steam over a pan of boiling water for 5-10 minutes until tender.
2. Then mash the flesh smooth or blitz in a food processor (you should have 200g).
3. Preheat the oven to 180°C.
4. Line a 20cm square cake tin with baking parchment. Whisk the butter and sugar in a large bowl with an electric whisk until pale and fluffy. Add the eggs, one at a time, with 1 tablespoon flour each time. Whisk in the remaining flour, the baking powder, cocoa, spices and sweet potato until combined and smooth.
5. Spoon the mixture into the tin and bake for 30-35 minutes until a skewer inserted in the centre comes out clean. Leave to cool in the tin for 10 minutes before turning out onto a wire rack to cool completely.
6. Meanwhile, heat the cream in a saucepan until just starting to boil. Remove from the heat and stir in the chocolate and orange zest. Leave for 5 minutes, then stir until smooth. Peel the orange and separate the segments. Dip each halfway into the ganache, then pop onto a sheet of baking paper to harden slightly.
7. Pour the remaining ganache over the cooled cake, then decorate with the orange segments. Will keep in an airtight container for 2-3 days.