Preheat the oven to 160 °C. Grease a 23-cm ring cake tin and dust with cake flour.
For the cake:
Cream the butter until soft. Gradually add the caster sugar, beating until the mixture is pale and fluffy. Add the eggs one by one, beating well after each addition.
Sift together the flour, baking powder and salt and gradually add about a third of the mixture to the butter mixture at a time. Add just enough milk to make a moderately stiff batter.
For the berry compote:
Bring the ingredients to the boil in a saucepan and cook until no longer runny. Leave to cool. Set aside a little for the icing. Spoon dollops of the batter into the prepared tin and spoon the rest of the compote on top.
Gently swirl a skewer through the mixture to create a marbled effect. Bake for 1 hour or until a skewer inserted in the middle of the cake comes out clean. Turn out on a wire rack. Leave to cool.
For the icing:
Heat the chocolate and butter in the microwave on high for about 1½ minutes. Add the yoghurt and mix in the reserved compote. Spoon over the cake and decorate with fresh berries and petals.
By Carmen Niehaus
Photographs: David Briers
Styling: Lisa Clark