Wash the Padron peppers and dry them thoroughly with paper towels. Puncture each pepper once with a toothpick to prevent them from bursting in the oil.

In a small bowl, whisk together the mayonnaise, yuzu juice, and soy sauce until smooth. Set the dip aside in the refrigerator.

Heat about 3 inches of vegetable oil in a heavy-bottomed pot or deep fryer to 350°F (175°C).

While the oil heats, prepare the batter. In a mixing bowl, combine the flour, cornstarch, egg yolk, and ice-cold sparkling water.

Mix the batter loosely with chopsticks or a fork. Do not overmix; small lumps of flour are desirable for a light, crispy texture.

Holding them by the stem, dip the peppers into the batter one by one, shaking off any excess so the coating is thin.

Carefully lower the peppers into the hot oil in small batches. Fry for 2-3 minutes until the batter is pale golden and crispy.

Remove the peppers with a slotted spoon and drain on a wire rack or paper towels.

Immediately sprinkle generously with sea salt flakes while the peppers are still hot.

Serve immediately alongside the chilled yuzu mayonnaise dipping sauce.