Open the oysters and clean the shells or ask your fishmonger to do this for you. To make the batter, whisk the flour with the cold water and fold in the stiffly whisked egg white and 1 tablespoon of olive oil. To make the dressing, whiz the tomatoes in a blender with the horseradish, garlic and vinegar. Add the hot pepper sauce and season with salt and pepper. Tweak the amounts of hot pepper sauce and vinegar to tast e¿ you want it to be hot and tangy. Pass the mixture through a fine sieve to remove any chunky bits. This will give you a nice smooth dressing. Check the seasoning.
Heat the vegetable oil in a deep-fat fryer to 350 degrees F (180 degrees C) and fry the arugula in small batches for about 25 seconds until nice and crisp. Remove and place on some kitchen paper. Drop each oyster into the batter, then remove with a spoon and fry for around 2 minutes until crisp and golden. Serve each oyster in its shell on a little fried rocket, drizzled with the tangy tomato dressing.
Try this: Place the shells on some cracked ice or a bed of coarse sea salt.
(c) Jamie Oliver 2002