Preheat the oven to 180C / 350F / 160 fan forced. Line an 8 inch square baking tin with baking paper.
FOR THE COOKIE DOUGH
Sift together the flour, cocoa, baking powder and salt.
Beat together the butter and sugar until very light and creamy.
Add half of the flour mix and beat until incorporated. Now add the milk and vanilla and beat until mixed through. Add the remaining flour mix and beat until it forms large crumbs.
Sprinkle two thirds of the cookie dough mix into the bottom of the baking tin, and then press down until the bottom of the pan is totally covered (if you slightly dampen your hands, it will make the job a bit easier, by not sticking to your hands).
FOR THE SIMPLE CHEESECAKE FILLING
Beat the cream cheese, sugar, sour cream, egg and vanilla until well mixed (a few small lumps are ok) - scrape down the sides of the bowl as necessary).
Add half of the chopped oreos to the cheesecake mixture and fold through, then pour and spread it over the cookie dough base.
Scatter over the remaining cookie dough in small clumps, followed by the remaining oreos, pressing them into the mix here and there.
Bake for around 35-40 minutes or until it is just set in the middle. Refrigerate for about 3 hours before serving.
I use a standard Australian 20ml tablespoon (4 teaspoons worldwide)
For best results you should always weigh ingredients like flour and sugar. Kitchen scales like these are relatively cheap but if you can’t weigh the ingredients, use the spoon and level method (don’t scoop).
All ovens vary - check for doneness 5-7 minutes before the recipe suggests.