Mix together the egg yolks, vanilla and water. Fit the dough tool. Place the butter and icing sugar in the bowl and mix until pale and fluffy. Add the egg yolk mixture, little by little. Sift together the flour, baking powder, salt and cinnamon. Add to the egg-butter mixture and mix again until the flour is fully incorporated. Add the chocolate chips, taking care not to over-work the dough.
Roll the dough into a cylinder on a clean worksurface.
Roll in icing sugar or cocoa powder or a mixture of both in equal quantities, wrap in clingfilm.
Refrigerate for at least 1 hour.
Cut the cylinder into 1cm slices to form cookies, arrange on a non-stick baking tray. Bake for approximately 10 minutes or until golden brown. Transfer to a wire rack to cool..