Preheat your oven to 190ºc/170ºc fan and line a 9x9inch square tin with parchment paper, and leave to the side for now.
Add the melted (or softened) butter to a bowl, and add the two sugars.
Add in the egg, and vanilla, and mix again.
Add the plain flour, bicarbonate, salt and cornflour and mix again until you have a cookie dough
Add the chocolate chips and mix with a spatula until distributed evenly
Add half of the mixture into the bottom of the tin and press down.
In a bowl, beat the cream cheese until loose, and add the sugar and beat again until combined. Gradually beat in the egg until combined along with the vanilla.
Pour the cheesecake mixture on top of the cookie bars, and then sprinkle and distribute over bits of the spare cookie dough.
Bake in the oven for 30 minutes. Once baked, leave to cool in the tin completely, and then refrigerate for a couple of hours to set
Notes
These cheesecake cookie bars will last for 3-4+ days in the fridge, once made
Sometimes they can still look a little underdone, but often baked cheesecake can do so. It will still have a ever so slight wobble, and when you touch it, it will spring back, but it shouldn’t be liquid by any means.