Thinly slice the mushrooms lengthwise (as shown in video and picture above).
In a shallow flat-bottom bowl, whisk together the potato starch, all-purpose flour, baking powder, garlic powder, white pepper, salt and 1 cup of cold water to make a slurry.
Add the neutral frying oil into a large frying pot until the oil is about 2 inches deep. Heat the oil over medium-high heat until it reaches 350°F.
Gently coat the mushrooms in the slurry batter and let any excess batter drip off. Gently lower the mushrooms into the oil. Deep-fry mushrooms for about 1-2 minutes on each side until they develop a golden color. They fry quickly so keep an eye on them! Transfer the friend mushrooms to a plate lined with paper towel or wire rack.
Season the fried mushroom with flaky salt and togorashi shichimi. Serve immediately with rice and curry.