In a small bowl, combine Japanese mayonnaise, soy sauce, and toasted sesame oil. Mix thoroughly until smooth and well blended. Cover the bowl and refrigerate until ready to serve.

Trim the base of the enoki mushrooms to separate them into smaller bunches. Gently wipe with a damp paper towel if needed. Do not wash them.

In a mixing bowl, whisk together tapioca flour, plain flour, ice cold water, and salt until smooth. Avoid overmixing to prevent a chewy texture.

Pour enough grapeseed oil into a deep pot or skillet to immerse the mushrooms. Heat over medium-high heat until it reaches 190°C (375°F). Test with a wooden chopstick for bubbles.

Dip small bunches of enoki mushrooms into the batter and fry them individually in the hot oil for 2-4 minutes until golden brown.

Use a slotted spoon to remove the fried mushrooms and place them on paper towels to drain excess oil. Serve immediately with sesame mayonnaise.