200g fine dark chocolate (70 per cent cocoa solids)
4 tbsp hot espresso
135g plain flour
a heaped tsp baking powder
3 tbsp good-quality cocoa powder
190g golden caster sugar
crème fraîche and poppy seeds, to serve
Lightly butter a 20cm loose-bottomed cake tin and line the base with a disc of baking parchment. Set the oven to 180C/gas mark 4.
Cook the beetroot, whole and unpeeled, in boiling unsalted water. Depending on their size, they will be knifepoint tender within 30 to 40 minutes. Young ones may take slightly less. Drain them, let them cool under running water, then peel them, slice out their stem and root, and blitz to a rough purée.
Melt the chocolate, snapped into small pieces, in a small bowl resting over a pot of simmering water. Don’t stir. When the chocolate looks almost melted, pour the hot coffee over it and stir once. Cut the butter into small pieces – the smaller the better –and add to the melted chocolate. Dip the butter down under the surface of the chocolate with a spoon (as best you can) and leave to soften.
Sift together the flour, baking powder and cocoa. Separate the eggs; put the whites in a mixing bowl. Stir the yolks together.
Now, working quickly but gently, remove the bowl of chocolate from the heat and stir until the butter has melted into the chocolate. Leave for a few minutes, then stir in the egg yolks. Do this quickly, mixing firmly so the eggs blend into the mixture. Fold in the beetroot. Whisk the egg whites until stiff, then fold in the sugar. Firmly but tenderly fold the beaten egg whites and sugar into the chocolate mixture. A large metal spoon is what you want; work in a deep, figure-of-eight movement but take care not to over-mix. Fold in the flour and cocoa.
Transfer quickly to the prepared cake tin and put in the oven, turning the heat down immediately to 160C/gas mark 3. Bake for 40 minutes. The rim of the cake will feel spongy, the inner part should still wobble a little when gently shaken.
Leave to cool (it will sink a tad in the centre), loosening it around the edges with a palette knife after half an hour or so. It is not a good idea to remove the cake from its tin until it is completely cold. Serve in thick slices, with crème fraîche and poppy seeds.
(original recipe from Nigel Slater).