Preheat the oven to 160°C. Grease and line a 20cm round baking tin with baking paper and set aside. Warm the oil in a medium-size saucepan on very low heat. Add the brown sugar, maple syrup and chocolate and stir until the chocolate is melted. Remove from heat. Add the grated beetroots.
Whisk the eggs in a small bowl and then add them to the saucepan. Sift the flour and cocoa powder together and stir into the beetroot mixture. Pour the batter into the tin and bake for 1 hour or until a skewer inserted comes out clean. Leave to cool for 5 minutes in the tin, before turning out and cooling completely.
To make the ganache, combine all ingredients in a small saucepan over low heat. Stir over medium-low heat, for 5 minutes or until the chocolate is melted and the mixture is smooth and glossy. Leave to cool for 5-10 minutes until the mixture thickens slightly and pour over the cake.