Prepare the tempura batter: in a mixing bowl, combine flour, cornstarch, and baking soda. Gradually add ice-cold water, mixing lightly until just combined; some lumps are okay. Keep batter cold.
2
Heat vegetable oil in a deep pot to 170°C (340°F).
3
Dip each ingredient (shrimp, sweet potato slices, green beans, bell pepper) into the batter, coating evenly.
4
Carefully drop the battered pieces into the hot oil, frying until golden and crispy, about 2-3 minutes per batch. Do not overcrowd the pan.
5
Remove with a slotted spoon and drain on paper towels.
6
Serve immediately with dipping sauces made from soy sauce and mirin, or your preferred condiments.