1.Using a vegetable peeler, cut carrots into long thin ribbons. Halve capsicums; discarding seeds and membranes. Cut capsicum into 2cm-thick slices. Cut onion into thin wedges.
2.For the wasabi aioli, blend or process egg yolks, juice, wasabi and garlic until smooth. With motor operating, add oil gradually in a thin stream; process until mixture thickens. Thin aioli with hot water, if desired.
3.Just before serving, whisk egg whites in small bowl until soft peaks form. Sift flours into large bowl. Stir in the water; fold in egg white.
4.Heat oil in wok. Dip vegetables, one piece at a time, in batter; deep-fry, in batches, until browned lightly and crisp. Drain on absorbent paper; keep each batch warm as you deep-fry remainder.
5.Serve tempura with separate bowls of soy sauce and wasabi aioli.