Preheat your oven to 180°C (350°F) and line two baking trays with parchment paper.

In a large mixing bowl, combine the cold butter chunks, brown sugar, and granulated sugar. Beat until combined but still clumpy, about 2-3 minutes.

Add in the large eggs and vanilla extract. Beat until incorporated while retaining some visible chunks of butter.

In a separate bowl, whisk together the flour, cornflour, and baking powder. Gradually add this to the wet ingredients, mixing until a stiff dough forms.

Fold in the chopped Kinder Bueno, Kinder chocolate, and chocolate chips until evenly distributed.

Divide the dough into 10-12 large clumps and place them on the trays, leaving space for spreading.

Chill the dough balls in the refrigerator for 30 minutes.

Bake for 15-20 minutes until slightly soft and golden around the edges. Optionally, top with additional chocolate pieces before finishing baking.

Let the cookies cool on the trays for about 5 minutes before transferring to a wire rack.