Add all the flour to a bowl. With the handle of a spoon, or a chopstick, mix, and stir in the ice-cold water until the mixture is slightly thicker than buttermilk consistency. Make a point of not mixing thoroughly, as tempura is renowned for lumps of flour.
Dip sliced vegetables (zucchini, onions, eggplants, carrots, bell peppers, sweet potatoes, string beans, broccoli, wild mushrooms, fresh herbs, and bok choy) any vegetables will work but these are the most commonly used) into the batter mixture and shake off any excess.
Deep fry vegetables in a wok or deep fat fryer (you can use a frying pan if you do not have anything else, you just need about 7cm/3 inches of clean oil) at 200C/400F/Gas 6 until the batter is light golden in color and crisp. (Any large amounts of hot oil in a kitchen, especially in woks which are not always that sturdy, scare me, please be careful and do not leave the pan unattended.) Turn the vegetables at intervals to ensure that both sides are cooked equally and then fish them out with a slotted spoon, shaking off any excess oil. Place them on kitchen paper towels and eat as soon as possible. The reason that I keep going on about eating them so quickly is because as your hot cooked vegetables cool down inside the batter they begin to steam, making them less crisp as time goes on. Good tempura should be crispy and is one of those things that should be made and cooked quickly and eaten straight away.
Pour the rice wine vinegar into a small bowl. Add the sugar and stir until the sugar is dissolved. Taste for sweetness. Add cilantro, chile, and garlic and mix well. Season with salt and pepper and allow to sit for 10 minutes to 1 hour, for flavors to combine.;
Recipe courtesy of Jamie Oliver