To Prep
Process the prawn flesh together with salt and sake in a food processor until you get a smooth paste.
Transfer to a mixing bowl and mix in the grated mountain potato, onion, egg, and potato flour.
Mix the ingredients well then chill the mixture in the fridge for at least 30 minutes.
To Cook
You’ll need an oil or candy thermometer for this as the frying temperature is key to getting a well fried fritter.
Heat up enough oil in a wok to 170°C. Shape the prawn mixture into balls and roll in the shiso leaves.
Drop the balls into the heated oil and deep-fry until the prawn is cooked all the way through. You’ll also want the shiso leaves to be crispy, but still retain their color.
Remove the seeds from the umeboshi and finely chop the flesh. Serve the prawn fritters with the chopped umeboshi flesh.