Step 1

Preheat oven to 180°C. Brush a square 20cm (base measurement) cake pan with melted butter to lightly grease. Line the base and 2 opposite sides with non-stick baking paper, allowing it to overhang.

Step 2

Combine the butter and chocolate in a saucepan over low heat. Cook, stirring, for 5 minutes or until chocolate melts and mixture is smooth. Remove from heat. Set aside for 5 minutes to cool.

Step 3

Whisk 2 of the eggs in a small bowl. Add whisked eggs and 140g (2/3 cup) of the sugar to the chocolate mixture, and stir to combine. Add the flour and sour cream and stir until well combined.

Step 4

Use an electric beater to beat the cream cheese and remaining sugar in a bowl until smooth. Add the remaining egg and beat until just combined.

Step 5

Spoon chocolate and cream cheese mixtures, alternately, over base of pan. Use a skewer to swirl to create a marble effect. Bake in oven for 30 minutes or until a skewer inserted into the centre comes out clean. Set aside in the pan for 1 hour to cool. Cut into squares to serve.