Begin by cleaning your oyster mushrooms carefully; avoid washing them in water to maintain their crispiness. Instead, use a damp cloth to wipe off any dirt. Trim off the tough ends and slice them into 2-3 cm strips.

In a medium-sized bowl, combine the egg (if using) with sweet potato starch, water, salt, and black pepper. Stir until you achieve a smooth and thick batter. For a vegan option, simply increase the amount of water and skip the egg, mixing until all ingredients are well incorporated.

Take each mushroom strip and immerse it in the batter, ensuring it is completely coated on all sides. Let any excess batter drip off slightly before placing them aside on a plate.

In a wok or deep frying pan, pour in approximately 4 cups of oil and heat it to a temperature of 170-180°C (340-356°F).

Fry the battered mushroom strips in batches, cooking for about 4-5 minutes, turning occasionally until lightly browned and crispy.

Increase the oil temperature to 200°C (392°F) for the final frying round. Quick-fry each batch for an additional 4-6 seconds for extra crispiness.

Use a slotted spoon to remove the deep-fried oyster mushrooms from the oil and place them on a plate lined with paper towels to drain excess oil. Season immediately and serve hot.