In a medium bowl combine together the flour, cornflour, bicarbonate of soda, and salt. Set aside.
Add the cream cheese into a large mixing bowl. Use a handheld electric mixer to beat the cream cheese until smooth and creamy.
Add the butter and beat until combined.
Tip in both sugars and beat on a medium-high speed until light and fluffy, around 2 minutes.
Add the egg and vanilla and mix for a further minute on a high speed.
Use a spatula to scrape down the sides and mix for a further few seconds to ensure everything is well combined.
Use a spatula to fold in the dry ingredients. When almost combined tip in around ¾ of both chocolate chunks and the crushed Oreos. Fold until the dry and wet ingredients are fully combined.
Cover and chill the dough for 1-2 hours in the fridge, or 30 minutes in the freezer. (The longer you chill the dough, the less the cookies will spread in the oven)
Roll the cookies into 10 equal sized balls. Press an oreo into each ball and mold the dough around it until completely covered. Roll back into a slightly flattened ball shape and arrange onto a lined baking sheet.
Press the remaining chocolate chunks onto the top of the cookies. Place into the freezer for 15 minutes whilst you preheat the oven 180℃/160℃ fan (350℉/320℉).
Arrange the cookie dough balls on lined baking trays with at least 3 inches between each ball. Bake for 13-14 minutes until lightly browned at the edges.
Allow the cookies to cool for 10 minutes on the baking trays before cooling completely on a wire rack.
Keep in an airtight container at room temperature for up to 1 week.
