Blanc de Saint-Pierre à la Crème de Petits Légumes

Skin a John Dory and cut it into fingersized fillets.

Cut a peeled carrot, leek and celery into a large julienne, and cook rapidly in a soupspoon of butter, a half cupful of water with a pinch of salt until al dente, and all liquid has boiled away. Keep warm.

Boil a large, peeled, diced