Preheat oven to 160°C fan forced. Grease and line the base and sides of a 22cm (base) round springform pan.
For the cake; combine eggs and sugar in a bowl. Using an electric mixer, beat on high speed for about 5 minutes or until thick and pale. Gently fold in the yoghurt, then olive oil. Sift the flour over the batter and gently fold until just combined. Pour into the prepared pan and smooth the top. Bake for 60-65 minutes, or until cooked when tested with a skewer. Stand in the pan for 15 minutes then transfer to a wire rack to cool. Wash and dry the pan.
Whip the cream, vanilla and 3 tablespoons of icing sugar to soft peaks. Fold in the yoghurt. Beat with a balloon whisk to firm peaks. Cut the cake horizontally in half. Return the base layer, cut-side up, to the unlined springform pan. Spread half the cream mixture over the base. Top with half the blueberries and 1 punnet of blackberries, pressing gently into the cream. Sandwich together with the top cake layer, cut-side down. Spread with remaining cream mixture. Cover loosely with plastic wrap and refrigerate overnight.
Spoon the remaining blueberries and 1 punnet of blackberries into a bowl. Sprinkle over the remaining 1 tablespoon of icing and toss gently to coat. Cover and refrigerate until ready to serve.
To serve, remove side of the pan. Transfer cake to a serving plate. Spoon over macerated berries and any juices. Serve.