Beat the softened butter with the sugar. Then add the vanilla and, one by one, the egg yolks, leaving the egg whites separate, as you have to beat them until stiff and add them later. Now add the flour, together with the baking powder and the cinnamon, sifting it all. Now add the milk and then the egg whites beaten until stiff. Remember to add the egg whites little by little, folding them in. Finally add the Nutella. Now spread the batter in the capsules and bake for approximately 20-23 minutes at 180ÂșC.