# To cook the beetroot, wrap each one in foil and place in a baking dish. Bake in the oven at 200ºC until soft (test by inserting a sharp knife). This can take anything from 45 minutes to 1½ hours, depending on the size of your beetroot.
# Remove from the oven, leave until cool enough to handle, unwrap the foil, then rub off the skins; they should come off easily (wear a pair of rubber gloves to keep your hands from turning pink if you like). Blitz the beetroot in a food processor until smooth.
# Grease and line a 23cm springform cake tin, leaving about 2cm of baking parchment above the rim of the tin, as the mixture rises quite high while baking.
# Preheat your oven to 180ºC.
# Put the chocolate and butter in a large heatproof bowl, fitted snugly over a pan of barely simmering water. Once the chocolate and butter have melted, remove from the heat and leave to cool.
# While the chocolate is cooling, whisk the egg yolks and sugar in another large bowl until light, pale and voluminous. This will take 4-5 minutes with a handheld electric mixer.
# Add the ground almonds, almond essence and puréed beetroot and stir to combine.
# Fold the chocolate mixture into the egg yolk and beetroot and stir gently until all the mixture is combined.
# Whisk the egg whites in a separate bowl until they form soft peaks, then, using a slotted metal spoon, fold a large spoonful of the egg whites into the chocolate mixture.
# Carefully combine it in until you can't see any white bits, then very gently fold in the rest, keeping as much air in the mixture as possible. Make sure no white bits remain.
# Bake in the oven for 40-45 minutes, until the mixture has risen well, and still has a bit of a bounce to it when pressed. It may have cracked slightly, this is normal.
# Remove from the oven, leave to cool completely in the tin on a wire rack before transferring to your serving plate.
# Dust over a mixture of cocoa powder and icing sugar to serve. It will sink slightly as there's no flour in the mixture and will be gooey in the middle if you eat it the same day, and slightly firmer after 24 hours. Serve with cream or crème fraîche.
* 250g whole beetroot, in their skins
* 400g good dark chocolate, broken into pieces
* 175g unsalted butter, diced
* 6 eggs, separated
* 175g caster sugar
* 25g ground almonds
* A few drops almond or vanilla essence