Step 1:Prepare the Dipping Sauce

• In a small saucepan, combine the dashi, soy sauce, mirin, and sugar.
• Bring to a gentle boil over medium heat, stirring until the sugar is dissolved.
• Remove from heat and set aside.

Step 2:Prepare the Tempura Batter

• In a large bowl, lightly beat the egg with ice-cold water.
• Add the all-purpose flour and cornstarch (if using) to the egg mixture. Stir very gently and briefly, just until combined. The batter should be lumpy and not over-mixed. This helps to create a light and crispy texture.

Step 3:Heat the Oil

• In a deep frying pan or pot, heat vegetable oil to 350°F (175°C). You can use a thermometer to check the temperature or drop a small piece of batter into the oil. If it sizzles and rises to the surface immediately, the oil is ready.

Step 4:Prepare the Ingredients

• Pat the vegetables and seafood dry with paper towels to remove excess moisture. This helps the batter stick better and prevents splattering during frying.

Step 5:Fry the Tempura

• Dip each piece of vegetable or seafood into the batter, allowing any excess to drip off.
• Carefully place the battered pieces into the hot oil. Fry in small batches to avoid overcrowding the pan, which can lower the oil temperature.
• Fry until the tempura is light golden and crispy, about 2-3 minutes for vegetables and 2-4 minutes for seafood.
• Remove the tempura with a slotted spoon or wire skimmer and drain on a paper towel-lined plate.

Step 6:Serve

• Arrange the tempura on a serving platter.
• Serve immediately with the dipping sauce (tentsuyu) on the side.