Preheat the oven to 180°C (350°F) and grease an 8" or 9" baking tin with butter or non stick cooking spray or line with baking paper and set aside.
Crush the Oreos and mix with the melted butter.
Press the Oreo crumbs in to the base of the baking pan and set aside while you make the cheesecake layer.
Beat the softened cream cheese until no lumps remain.
Beat in the Greek yoghurt and egg until smooth.
Beat in the icing sugar and vanilla extract and beat until smooth.
Lightly crush the Oreos and stir those through the cheesecake mixture.
Pour the cheesecake mixture over the Oreo base and set aside.
Cookie dough layer;
Melt the butter and beat that with the brown sugar and sugar.
Add in the eggs and vanilla essence and beat until smooth.
Add in the flour and baking powder and mix.
Finally add the chocolate chips and mix together.
Dollop the cookie dough over the cheesecake layer and then place in the oven for 30-35 minutes until the cookie dough is lightly brown and the top feels dry and firm and the pan is set. You can give it a little shake to see if it is set.
Move bars to a cooling rack and allow to cool completely.
Cut into squares and store in an airtight container in the fridge for up to a week.
Serve at room temperature or cold. Both are delicious.