In a large bowl sift the flour, cornstarch, cocoa powder, baking powder and bicarb soda. Mix together and set aside.
In another large bowl beat the butter until pale and fluffy, before beating in both sugars. Add the eggs and vanilla & beat until well combined.
Add the flour mixture into the butter/eg mixture and fold until flour streaks just disappear. Fold through the choc chips and hazelnuts.
Divide the dough into 12 portions (From memory like ~140g each?). Flatten a portion, add a big spoon of nutella in the centre and a Ferrero Rocher. Encase the nutella/ferrero rocher with dough, ensure there is no holes or the filling will melt out. Either refrigerate (I prefer this) or bake straight away.
BAKING STRAIGHT AWAY: Preheat the oven to 200ºC. Bake 6 cookies at a time for 10 minutes.
REFRIGERATION: Refrigerate for 24-72 hours. Refrigeration makes a thicker cookie that doesn't spread a much, is crispy on the outside and moist on the inside.Preheat the oven to 200ºC. Bake 6 cookies at a time for 13-14 minutes. Run a bowl or cookie cutter around each cookie straight out the oven to smooth the edges/make them more circular.
