Use two large spring-form tins, 26cm in diameter, 7cm deep.
Boil, peel and blend about 800g beetroots. Weigh 780g of the purée and allow to cool slightly.
Melt the chocolate in a bain-marie. Mix the sugar, vanilla, eggs and oil. Sieve the flour, baking powder and cocoa powder into the sugar, egg, oil mix. Blend together with the purée.
Fold the melted chocolate into the mix. Add the crème fraîche, cocoa nibs and salt. Divide between the two cake tins. Bake at 170oC for about 45 minutes.
Bring the cream, sugar and glucose to the boil.
Pour over the chocolate and stir until smooth. Spread the glaze evenly over the cake and sprinkle with Oialla nibs.