- Preheat the oven to gas 4, 180°C, fan 160°C; grease and line a 900g loaf tin with nonstick baking paper. Purée the beetroot in a food processor or with a stick blender; set aside. Melt the chocolate in a heatproof bowl in the microwave in 30 sec bursts for 1-2 mins or until melted. Cool for 5 mins.
- Put the sugar, oil, eggs and vanilla in a mixing bowl and whisk with an electric whisk for 2 mins until well combined and the sugar isn’t as grainy, then stir in the chocolate and blitzed beetroot until combined. In a separate bowl, sift together the flour, ground almonds, cocoa and baking powder, then briefly whisk into the wet ingredients until just combined. Spoon into the prepared tin, level, then bake for 1 hr or until a knife inserted in the centre comes out clean. Leave to cool in the tin for 20 mins, then transfer the cake in the paper to a wire rack to cool completely.
- Meanwhile, make the drizzle. Put 125g blackberries, the beetroot, thyme (if using) and sugar in a medium saucepan, set over a medium-high heat and simmer, stirring regularly, for 5-7 mins until the liquid has thickened. Discard the thyme sprigs and push everything else through a fine sieve into a bowl. Leave to cool completely.
- To make the icing, whisk the mascarpone, icing sugar and vanilla in a mixing bowl for 1-2 mins until thick enough to hold its shape, then swirl over the cooled cake. Drizzle over the blackberry and beetroot sauce and top with the remaining blackberries and extra thyme sprigs, if you like.
Tip: Wrap the cooled cake, uniced, in clingfilm and store in an airtight container for up to 3 days. Or ice, then store in the fridge for up to 4 days.
Freezing and defrosting guidelines
Freeze undecorated cake only. In order to enjoy optimum flavour and quality, frozen items are best used within 3 months of their freezing date. For more tips on freezing and defrosting food, read our article Love Your Freezer.
See more Chocolate cake recipes
This recipe was updated to include steps for adding the beetroot and melted chocolate to the batter.