1. To make the dipping sauce, put the sake, soy sauce, sugar, and 2 tbsp water in a small bowl, stir together, then set aside.

2. Pour in oil to a depth of 3 in (7.5cm) in a heavy-bottomed saucepan. Heat over high heat to 375°F (190°C). Meanwhile, lightly whisk together the flour, cold water, and egg yolk in a bowl. The batter should remain lumpy, which is what makes the tempura light.

3. Preheat the oven to 200°F (100°C). Working in batches, dip the vegetable pieces into the batter, letting any excess batter drip back into the bowl. Carefully add the battered vegetables to the hot oil and deep-fry for 1–2 minutes on each side, or until golden brown. Use a slotted spoon to remove them from the pan and drain well on paper towels. Keep warm in the oven while frying the remaining vegetables.

4. Serve immediately with small bowls of the dipping sauce for each diner.