Start by making a basic herb oil. To do this blitz a large handful of herbs with your oil. Then warm both in a small pan. Turn off as the oil starts to reach boiling point and allow to cool. Strain through a fine sieve and set to one side.
For the cod heat your oil in a non-stick frying pan. Place your cod into the pan and cook for 2-3 mins before adding in your diced butter. Turn your fish over carefully with a fish slice and then spoon the bubbling golden truffle butter over the fish as it cooks. Cook until the fish starts to flake and then serve.
Garnish the plate with a bunch of washed watercress, drizzle of herb oil and a pinch of sea salt.