Cooking cod in a frying pan or oven takes skill, but by using a temperature-controlled water bath anyone can produce a perfectly cooked portion of cod. Cooking the fish under vacuum helps to trap the moisture inside the cod and the constant, low temperature of the water ensures the fillet cooks evenly.
To add a caramelised flavour to the fish, quickly fry it in a hot frying pan until coloured. Be sure to do this quickly, however, or the fish will overcook.
Other ingredients can be added to the bag with the cod to impart flavour while it cooks. Andy McLeish keeps it simple by adding some olive oil but a concentrated fish stock or white wine sauce are both delicious alternatives.