Preheat oven to 200 degrees C and grease a 25cm springfrom cake tin.
In a mixing bowl combine butter, cream cheese, 1/2 cup sugar, 1 egg, flour and baking powder. Mix well and pour into cake tin. Arrange the berries over the top. To the mixing bowl add yoghurt, cornflour, remaining sugar, vanilla and two egg yolks. Whisk well and spread over the top of the cake.
Bake until the crust is brown around the edges, about 30 minutes. Serve chilled.