For the tomato vinaigrette:
Skin and pin bone the cod fillets, and put them in a dish where they can be laid out flat. Cover them with Maldon salt and put the dish aside for 45 minutes. Take the fillets out, shake off as much salt as possible, then rinse the fish under running water.
Put the milk, thyme and bayleaf in a large pan over a medium heat and poach the cod; how long this takes will depend on the thickness of the fillets, but it shouldn’t be longer than 6 minutes. Remove the cod from the poaching liquor and drain off any excess.
Make the tomato vinaigrette when you are ready to serve. Combine the tomatoes, thyme sprigs, tomato juice and sherry vinegar in a liquidiser (or use a hand blender). Then gradually add the oil. Pass the liquid through a fine sieve and use immediately, pouring a little around the pieces of fish.
Tip: At the Mason’s Arms, we serve this dish with crushed new potatoes and chorizo julienne. Just before serving we add the julienne of chorizo to the potato and put the potato in the middle of the plate, then place the cod on top of the potato, with the tomato vinaigrette around it. A little Maldon salt is sprinkled over everything, and it is garnished with a few rocket leaves.