Celeriac and Anchovy Gratin

I adore celeriac, that beautiful monstrosity with its stringy skin, its whorled and bumpy exterior – rather like an albino coconut – that hides the secret of its creamy turnip-like flesh within (and you can admire its portrait on). It tastes delicately of celery, but a nutty, parsley-ish celery, more herbal than aniseedy. It is a generous partner to so many ingredients (see the Soupy Rice with Celeriac and Chestnuts on and the