Cream the butter and sugars

• Beat the softened butter with the brown sugar and caster sugar until pale and fluffy.
• Beat in the egg and vanilla extract until fully combined.

Make the cookie dough

• Add the plain flour, baking soda, cornflour and salt and mix to a soft dough.
• Fold in the chopped Kinder bars and milk chocolate chunks.

Shape and chill

• Divide the dough into equal balls and flatten each slightly.
• Press a hollow in the centre, add a spoon of chilled hazelnut spread and seal the dough around it.
• Chill the cookie dough balls in the fridge.

Bake

• Place the cookie dough balls on a lined baking tray, spaced apart.
• Bake at 180 °C until the edges are set and the centres still soft.

Cool and serve

• Leave the cookies on the tray to firm up, then transfer to a rack.
• Serve slightly warm so the chocolate is gooey.