Preheat oven to 170°C. Line a 16cm x 26cm (base) slab pan with non-stick baking paper.

For the cheesecake mixture, use an electric beater to beat cream cheese and sugar until smooth. Beat in the eggs. Stir in vanilla extract and flour.

For the chocolate mixture, melt the chocolate and butter in a medium microwave-safe bowl on Medium/50% power, stirring every minute for 1-2 minutes. Cool slightly. Add the sugar and eggs, and mix well. Stir in the flour.

Spoon cheesecake mixture and chocolate mixture alternately into the pan. Make a swirled pattern with a fine skewer. Bake 20-25 minutes or until crumbs cling to a skewer when inserted. Set aside to cool completely.