Ingredients

Step by step

1. Preheat the oven to 200°C, fan 180°C, gas 6. Wrap the beetroot chunks in a foil parcel, place in a dish and roast for 1 hour, or until tender. Remove, open up the foil and leave to cool.
2. Reduce the oven to 180°C, fan 160°C, gas 4 and line a 900g loaf tin (about 10cm x 20cm base) loaf tin. Put two- thirds of the cooled beetroot in a food processor with the blackberries, lemon juice, vinegar and vanilla and blitz until you have a smooth purée. Stir through the buttermilk and set aside.
3. Beat the butter and sugar together until light and fluffy, then add the eggs one at a time, beating well between each addition.
4. Sift together the flour, baking powder and cocoa powder, then fold through the mix, alternating with the beetroot purée, until well combined. Transfer to the tin and bake for 50 minutes, or until a skewer comes out clean. Cool in the tin for 15 minutes, before removing to a wire rack to cool completely.
5. For the candied beetroot, chop the remaining beetroot into small cubes. Dissolve 50g of caster sugar in 50ml water in a small pan. Add the beetroot cubes and simmer for 10 minutes. Remove the cubes to a plate lined with baking paper; leave to cool.
6. For the blackberry syrup, blitz 150g of the blackberries in a food processor until smooth. Pass through a sieve into a small pan and add the remaining 20g of sugar. Heat gently to dissolve the sugar then simmer for 5 minutes or until syrupy. Leave to cool.
7. To make the frosting, beat the butter with the icing sugar until smooth. Add the mascarpone and vanilla and beat until combined.
8. Pipe or swirl the icing over the top of the cake and decorate with the reserved blackberries, candied beetroot and cooled blackberry syrup. The cake keeps for up to 3 days in an airtight container.