Prepare the Purple Sauce (This can be prepared ahead and set aside at cool room temperature for 1 hour, or refrigerated.) For the purple sauce, place the mayonnaise, lemon juice, vinegar, sugar, soy sauce and ginger in a food processor fitted with chopping blade. Process until mixed and smooth, pulsing on/off. With the machine running, pour in oil in a slow, thin stream. Add the cabbage and process, pulsing on/off and occasionally scraping down the sides of the container, until finely ground and almost smooth. Season with salt and pepper. (This can be prepared 1 day ahead, transferred to a bowl, covered and refrigerated until 30 minutes before serving.) Line a large baking sheet with parchment paper. Pull the kataifi out of the bag and cut it into 3 cm pieces over a bowl. Separate the threads with your fingers. Refrigerate or refreeze the remaining kataifi for another dish. Place the kataifi on 1 large plate and the flour on another. Whisk the egg with water in a soup plate until blended. Season the egg with salt and pepper. One at a time, dip the shrimp into the flour until well coated, patting off excess. Hold the shrimp with tongs and dip it into the egg, coating completely, and then into the kataifi. Place the shrimp dipped kataifi in the palm of your hand and compress it into a large neat package, about 6 cm in diameter. Place on the prepared baking sheet. Repeat with the remaining shrimp. (This can be prepared ahead and set aside, covered, at cool room temperature for 1 hour or refrigerated until 1 hour before frying.) To cook, line a large baking sheet with paper towels. Heat 3 cm of oil in a wok or a large skillet to 180ºC , or until bubbles form around a chopstick or a wooden spoon handle immersed in the oil. Using tongs, gradually dip 1 shrimp into the oil, waiting until the bottom layer of the kataifi sets before immersing the shrimp completely. Add additional shrimp in the same manner in batches without crowding. Cool the shrimp until golden brown on both sides, for about 3 minutes total. Transfer to paper towels with tongs or a slotted spoon. (This can be cooked several hours ahead. Reheat on towel lined tray in a preheated 230ºC oven for 2 to 3 minutes.) To serve, spoon the Purple Sauce in the center of 4 large plates. Arrange 4 shrimp on top of the sauce on each plate. Serve immediately.