To make the escabeche, pour the extra virgin olive oil into a hot frying pan and cook the onion, currants and garlic for a few minutes. Add the carrot, chillies, marjoram, bay leaves and spices and carry on cooking until the carrot takes on a little colour and the currants are puffed up and golden.
Pour in the stock, cider vinegar and sherry and bring to the boil. Reduce the heat and simmer briskly for around five minutes for the flavours to combine. Season with salt, pepper and a good pinch of brown sugar, if you think it needs it, and add the radishes.
While the sauce is cooking, prepare the sardines. Dust the sardine fillets in seasoned polenta. Heat two to three tablespoons of the olive oil in a large, non-stick frying pan and cook the sardine fillets in two or three batches for just 1 to 2 minutes on each side until they have a lovely golden crust, adding extra oil if necessary.
Drain on kitchen paper and transfer to a shallow dish.
Spoon the escabeche over the sardine fillets and leave to infuse for half an hour.
Sprinkle with the pine nuts and chopped parsley just before serving and have lots of crusty bread around to mop up the deliciously piquant juices.