226 g (1 cup) unsalted butter, cut into cubes, plus extra for greasing
250g (9 oz) beets, peeled and halved
250g (9 oz) dark chocolate (at least 70% cocoa solids), chopped into pieces
3 large eggs
1 tsp vanilla bean paste
200g (1 cup) turbinado (or Demerera) sugar
150g (1¼ cups) self-raising flour
Sea salt