Heat the oil in a deep, heavy-bottomed pan. The oil is ready when a breadcrumb dropped into it will sizzle gently. (CAUTION: Hot oil can be very dangerous. Do not leave unattended.)
Place the flour and the sparkling water into a large bowl and whisk until a smooth batter is formed.
Dip the mangetout, carrots and sweetcorn into the batter and carefully place into the oil and deep-fry for two minutes, or until crisp and golden. Carefully remove with a slotted spoon and drain on kitchen towels.
Meanwhile, for the sauce, place all the ingredients, except the ginger, into a small saucepan over a medium heat. Bring to the boil and reduce the heat to simmer for three minutes.
Place into a food processor and blend until smooth. Transfer to a serving bowl and stir through the ginger.
To serve, place the tempura vegetables into a bowl and serve the sauce alongside.
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