Add the unsalted butter, light brown soft sugar and white granulated sugar to a bowl and beat together until creamy - I use my stand mixer with the beater attachment.
Add in the egg, egg yolk, and vanilla extract and beat again.
Add in the plain flour, cornflour, bicarbonate of soda, and salt and beat until a thick cookie dough is formed!
Add in the chocolate chips and beat the cookie dough again until distributed well!
Split the cookie dough into three equal portions (about 475g each).
Line the bottom of a 8" springform cake tin (at least 2.75" in depth).
Press the first third of cookie dough onto the bottom of the cake tin.
Press the second third of cookie dough around the sides of the cake tin evenly.
Melt the white chocolate hazelnut spread for 20 seconds in the microwave to loosen slightly or mix in a bowl briefly to loosen. Pour into the cake tin inside the cookie dough case!
Press the Kinder chocolate/Kinder Bueno into the spread. Freeze the pie at this stage for an hour.
Once frozen, cover the top of the Kinder Cookie Pie with the final third of cookie dough, making sure to seal it well!
Freeze the Kinder Cookie Pie for another hour whilst you preheat the oven to 200°c for a regular oven, or 180°c for a fan oven like me.
Once chilled and the oven preheated, bake the Kinder Cookie Pie for 30 minutes until the pie is lovely and golden on top. Leave to cool outside of the oven for an hour and do NOT remove from the tin.
Once cooled for an hour, put the Kinder Cookie Pie in the fridge and chill for 5-6 hours (or preferably overnight!)
Once it has been chilled, carefully remove from the tin!
Using a large and sharp knife, portion the Kinder Cookie Pie!